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1

2006 Nature Publishing Group Graphene-based composite materials  

E-print Network

for the preparation of graphene-polymer composites via complete exfoliation of graphite9 and molecular not readily exfoliate to yield individual graphene sheets. Here we present a general approach. 1a). In contrast to pristine graphite, the graphene- derived sheets in graphite oxide (graphene

2

Composite Materials  

NASA Technical Reports Server (NTRS)

Langley Research Center researchers invented an advanced polymer, a chemical compound formed by uniting many small molecules to create a complex molecule with different chemical properties. The material is a thermoplastic polyimide that resists solvents. Other polymers of this generic type are soluble in solvents, thus cannot be used where solvents are present. High Technology Services (HTS), Inc. licensed technology and is engaged in development and manufacture of high performance plastics, resins and composite materials. Techimer Materials Division is using technology for composite matrix resins that offer heat resistance and protection from radiation, electrical and chemical degradation. Applications of new polymer include molding resins, adhesives and matrix resins for fiber reinforced composites.

1988-01-01

3

Composite Materials  

NASA Technical Reports Server (NTRS)

Composites are lighter and stronger than metals. Aramid fibers like Kevlar and Nomex were developed by DuPont Corporation and can be combined in a honeycomb structure which can give an airplane a light, tough structure. Composites can be molded into many aerodynamic shapes eliminating rivets and fasteners. Langley Research Center has tested composites for both aerospace and non-aerospace applications. They are also used in boat hulls, military shelters, etc.

1985-01-01

4

Production of natural and synthesized aluminum-based composite materials with the aid of ultrasonic (cavitation) treatment of the melt.  

PubMed

The application of ultrasonic melt treatment to the production of natural and synthesized aluminum-based composite materials is considered in terms of underlying basic ideas and commercial implementations. It is shown that the ultrasonic cavitation treatment combined with microalloying of hypereutectic Al-Si natural composites (alloys) promotes the formation of structures suitable for further deformation. The use of highly impure starting materials becomes also possible. The combination of ultrasonic cavitation treatment with electromagnetic stirring allows one to considerably improve the size and spatial distribution of ceramic particles in metal-matrix composites. PMID:12818397

Eskin, G I; Eskin, D G

2003-07-01

5

Composite Materials Handbook  

NSDL National Science Digital Library

From the US Army Research Laboratory, Materials Sciences Corporation, and University of Delaware Center for Composite Materials, the Composite Materials Handbook provides the "information and guidance necessary to design and fabricate end items from composite materials." Along with current information on the material properties of these composite materials, the handbook also includes data development and usage guidelines. The information has been divided into three areas: polymer, metal, and ceramic matrix composites. The Polymer Matrix Composites Handbook (three volumes including Guidelines for Characterization of Structural Materials; Material Properties; and Materials Usage, Design, and Analysis) and the Metal Matrix Composites Handbook (one volume, .pdf) are available here. The Ceramic Matrix Composites Handbook has yet to be completed. Users may also download Quick Composites Data in spreadsheet format.

6

Preparation of antibacterial composite material of natural rubber particles coated with silica and titania  

NASA Astrophysics Data System (ADS)

Silica coating, followed by titania coating, was performed over spray-dried natural rubber (NR) compound for physical and anti-bacterial characterizations. Titania has a strong photo-oxidative catalytic property, which can disinfect bacteria, but may degrade NR. Therefore, silica coating was intended to form a barrier between NR and titania. First, NR particles were prepared by spray-drying of NR compound latex, formulated for household glove products, mixed with sodium dodecyl sulfate (SDS) to reduce particle agglomeration. The factorial experimental design was employed to investigate the effects of nozzle flow rate (500-700 Lh-1), inlet air temperature (110-150 °C), SDS content (35-55 phr) and mass flow rate (1.2-1.7 g rubber/min) on NR yield and moisture content. Then, the NR compound particles prepared at the optimum condition were coated with silica, using tetraethoxysilane (TEOS) as the precursor, by chemical vapor deposition (CVD) at 60 °C for 2-48 hours. Next, the particles were coated with titania using titanium tetrafluoride (TiF4) by liquid phase deposition (LPD) at 60 ºC for 4-8 hours. The NR composites were characterized for surface morphology by SEM, silica and titania content by TGA and EDX. The NR composites were found to cause more than 99% reduction of Escherichia coli and Staphylococcus aureus under 1-hour exposure to natural light.

Wisutiratanamanee, Apisit; Poompradub, Sirilux; Poochinda, Kunakorn

2014-06-01

7

Composite structural materials  

NASA Technical Reports Server (NTRS)

Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

Loewy, R. G.; Wiberley, S. E.

1985-01-01

8

Tough Composite Materials  

NASA Technical Reports Server (NTRS)

Papers and working group summaries are presented which address composite material behavior and performance improvement. Topic areas include composite fracture toughness and impact characterization, constituent properties and interrelationships, and matrix synthesis and characterization.

Vosteen, L. F. (compiler); Johnson, N. J. (compiler); Teichman, L. A. (compiler)

1984-01-01

9

Composite structural materials  

NASA Technical Reports Server (NTRS)

Technology utilization of fiber reinforced composite materials is discussed in the areas of physical properties, and life prediction. Programs related to the Composite Aircraft Program are described in detail.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1979-01-01

10

Composite structural materials  

NASA Technical Reports Server (NTRS)

A multifaceted program is described in which aeronautical, mechanical, and materials engineers interact to develop composite aircraft structures. Topics covered include: (1) the design of an advanced composite elevator and a proposed spar and rib assembly; (2) optimizing fiber orientation in the vicinity of heavily loaded joints; (3) failure mechanisms and delamination; (4) the construction of an ultralight sailplane; (5) computer-aided design; finite element analysis programs, preprocessor development, and array preprocessor for SPAR; (6) advanced analysis methods for composite structures; (7) ultrasonic nondestructive testing; (8) physical properties of epoxy resins and composites; (9) fatigue in composite materials, and (10) transverse thermal expansion of carbon/epoxy composites.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1979-01-01

11

Composite structural materials  

NASA Technical Reports Server (NTRS)

The purpose of the RPI composites program is to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, reliability and life prediction. Concommitant goals are to educate engineers to design and use composite materials as normal or conventional materials. A multifaceted program was instituted to achieve these objectives.

Ansell, G. S.; Wiberley, S. E.

1978-01-01

12

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

Clough, Roger L. (Albuquerque, NM); Sylwester, Alan P. (Albuquerque, NM)

1989-01-01

13

Composite Structural Materials  

NASA Technical Reports Server (NTRS)

The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.

Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

1984-01-01

14

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Clough, R.L.; Sylwester, A.P.

1989-05-23

15

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Clough, R.L.; Sylwester, A.P.

1988-06-20

16

Composite structural materials  

NASA Technical Reports Server (NTRS)

Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

Loewy, R.; Wiberley, S. E.

1986-01-01

17

Composite Material Switches  

NASA Technical Reports Server (NTRS)

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Javadi, Hamid (Inventor)

2001-01-01

18

Composite Material Switches  

NASA Technical Reports Server (NTRS)

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Javadi, Hamid (Inventor)

2002-01-01

19

Mechanics of Composite Materials  

Microsoft Academic Search

The mechanical behavior of composites is traditionally evaluated on both microscopic and macroscopic scale to take into account inhomogeneity. Micromechanics attempts to quantify the interactions of fiber and matrix (reinforcement and resin) on a microscopic scale on par with the diameter of a single fiber. Macromechanics treats composites as homogeneous materials, with mechanical properties representative of the laminate as a

Robert M. Jones

1999-01-01

20

Composite structural materials  

NASA Technical Reports Server (NTRS)

Progress and plans are reported for investigations of: (1) the mechanical properties of high performance carbon fibers; (2) fatigue in composite materials; (3) moisture and temperature effects on the mechanical properties of graphite-epoxy laminates; (4) the theory of inhomogeneous swelling in epoxy resin; (5) numerical studies of the micromechanics of composite fracture; (6) free edge failures of composite laminates; (7) analysis of unbalanced laminates; (8) compact lug design; (9) quantification of Saint-Venant's principles for a general prismatic member; (10) variation of resin properties through the thickness of cured samples; and (11) the wing fuselage ensemble of the RP-1 and RP-2 sailplanes.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1983-01-01

21

Composite ion exchange materials  

SciTech Connect

Composite ion exchange materials can be formed by sorbing ion exchange polymers on inert, high surface area substrates. In general, the flux of ions and molecules through these composites, as measured electrochemically, increases as the ratio of the surface area of the substrate increases relative to the volume of the ion exchanger. This suggests that fields and gradients established at the interface between the ion exchanger and substrate are important in determining the transport characteristics of the composites. Here, the authors will focus on composites formed with a cation exchange polymer, Nafion, and two different types of microbeads: polystyrene microspheres and polystyrene coated magnetic microbeads. For the polystyrene microbeads, scanning electron micrographs suggest the beads cluster in a self-similar manner, independent of the bead diameter. Flux of Ru(NH3)63+ through the composites was studied as a function of bead fraction, bead radii, and fixed surface area with mixed bead sizes. Flux was well modeled by surface diffusion along a fractal interface. Magnetic composites were formed with columns of magnetic microbeads normal to the electrode surface. Flux of Ru(NH3)63+ through these composites increased exponentially with bead fraction. For electrolyses, the difference in the molar magnetic susceptibility of the products and reactants, Dcm, tends to be non-zero. For seven redox reactions, the ratio of the flux through the magnetic composites to the flux through a Nafion film increases monotonically with {vert_bar}Dcm{vert_bar}, with enhancements as large as thirty-fold. For reversible species, the electrolysis potential through the magnetic composites is 35 mV positive of that for the Nafion films.

Amarasinghe, S.; Zook, L.; Leddy, J. [Univ. of Iowa, Iowa City, IA (United States)

1994-12-31

22

Aerogel/polymer composite materials  

NASA Technical Reports Server (NTRS)

The invention provides new composite materials containing aerogels blended with thermoplastic polymer materials at a weight ratio of aerogel to thermoplastic polymer of less than 20:100. The composite materials have improved thermal insulation ability. The composite materials also have better flexibility and less brittleness at low temperatures than the parent thermoplastic polymer materials.

Williams, Martha K. (Inventor); Smith, Trent M. (Inventor); Fesmire, James E. (Inventor); Roberson, Luke B. (Inventor); Clayton, LaNetra M. (Inventor)

2010-01-01

23

Advanced composite materials and processes  

NASA Technical Reports Server (NTRS)

Composites are generally defined as two or more individual materials, which, when combined into a single material system, results in improved physical and/or mechanical properties. The freedom of choice of the starting components for composites allows the generation of materials that can be specifically tailored to meet a variety of applications. Advanced composites are described as a combination of high strength fibers and high performance polymer matrix materials. These advanced materials are required to permit future aircraft and spacecraft to perform in extended environments. Advanced composite precursor materials, processes for conversion of these materials to structures, and selected applications for composites are reviewed.

Baucom, Robert M.

1991-01-01

24

Processing composite materials  

NASA Technical Reports Server (NTRS)

The fabrication of several composite structural articles including DC-10 upper aft rudders, L-1011 vertical fins and composite biomedical appliances are discussed. Innovative composite processing methods are included.

Baucom, R. M.

1982-01-01

25

Accelerated Insertion of Materials - Composites.  

National Technical Information Service (NTIS)

The objective of the Accelerated Insertion of Materials - Composites (AIM-C) program is to develop and validate new approaches for materials development that will accelerate the insertion of materials into production hardware.

G. Havskjold

2001-01-01

26

Notched Strength of Composite Materials  

Microsoft Academic Search

A macroscopic model for predicting the strength of a composite laminate containing a circular notch is introduced. A property, which quantifies the reduction in strength of a given composite material or laminate due to a circular notch, is proposed. The superposition of notched strength data for several important composite material systems and laminate stacking sequences is achieved through development of

R. Byron Pipes; Robert C. Wetherhold; John W. Gillespie

1979-01-01

27

On free vibrations of a composite material circular cylindrical shells  

NASA Astrophysics Data System (ADS)

The natural vibrations of a thin walled circular cylindrical shell composed of specially orthotropic composite materials are studied in detail. The work of Koga (1988) for isotropic shells is extended to shells of composite materials. The results are easy to use solutions for the natural frequencies for the composite shell expressed in terms of the natural frequencies for beams with the same boundary conditions at the ends, modified to include the effects of the shell geometry and the anisotropic composite material properties.

Fisher, Christopher A.; Vinson, Jack R.

1993-04-01

28

Composite material and method for production of improved composite material  

NASA Technical Reports Server (NTRS)

A laminated composite material with improved interlaminar strength and damage tolerance having short rods distributed evenly throughout the composite material perpendicular to the laminae. Each rod is shorter than the thickness of the finished laminate, but several times as long as the thickness of each lamina. The laminate is made by inserting short rods in layers of prepreg material, and then stacking and curing prepreg material with rods inserted therethrough.

Farley, Gary L. (Inventor)

1996-01-01

29

Natural Fiber Composites: A Review  

SciTech Connect

The need for renewable fiber reinforced composites has never been as prevalent as it currently is. Natural fibers offer both cost savings and a reduction in density when compared to glass fibers. Though the strength of natural fibers is not as great as glass, the specific properties are comparable. Currently natural fiber composites have two issues that need to be addressed: resin compatibility and water absorption. The following preliminary research has investigated the use of Kenaf, Hibiscus cannabinus, as a possible glass replacement in fiber reinforced composites.

Westman, Matthew P.; Fifield, Leonard S.; Simmons, Kevin L.; Laddha, Sachin; Kafentzis, Tyler A.

2010-03-07

30

NATURAL FIBER OR GLASS REINFORCED POLYPROPYLENE COMPOSITES?  

SciTech Connect

Problems related to the recycle of conventional composite materials are becoming always more relevant for many industrial fields. Natural fiber composites (NFC) have recently gained much attention due to their low cost, environmental gains (eco-compatibility), easy disposal, reduction in volatile organic emissions, and their potential to compete with glass fiber composites (GFC). Interest in natural fibers is not only based over ecological aspects. NFC have good mechanical performances in relation to their low specific weight and low price. A characterization of mechanical properties, dynamic behavior, and moisture absorption is presented.

Lorenzi, W.; Di Landro, L.; Casiraghi, A.; Pagano, M. R. [Dipartimento di Ingegneria Aerospaziale, Politecnico di Milano (Italy)

2008-08-28

31

Natural Fiber or Glass Reinforced Polypropylene Composites?  

NASA Astrophysics Data System (ADS)

Problems related to the recycle of conventional composite materials are becoming always more relevant for many industrial fields. Natural fiber composites (NFC) have recently gained much attention due to their low cost, environmental gains (eco-compatibility), easy disposal, reduction in volatile organic emissions, and their potential to compete with glass fiber composites (GFC). Interest in natural fibers is not only based over ecological aspects. NFC have good mechanical performances in relation to their low specific weight and low price. A characterization of mechanical properties, dynamic behavior, and moisture absorption is presented.

Lorenzi, W.; Di Landro, L.; Casiraghi, A.; Pagano, M. R.

2008-08-01

32

Composite structural materials  

NASA Technical Reports Server (NTRS)

The composite aircraft program component (CAPCOMP) is a graduate level project conducted in parallel with a composite structures program. The composite aircraft program glider (CAPGLIDE) is an undergraduate demonstration project which has as its objectives the design, fabrication, and testing of a foot launched ultralight glider using composite structures. The objective of the computer aided design (COMPAD) portion of the composites project is to provide computer tools for the analysis and design of composite structures. The major thrust of COMPAD is in the finite element area with effort directed at implementing finite element analysis capabilities and developing interactive graphics preprocessing and postprocessing capabilities. The criteria for selecting research projects to be conducted under the innovative and supporting research (INSURE) program are described.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1981-01-01

33

Composite materials: A compilation  

NASA Technical Reports Server (NTRS)

Design, analysis and fabrication techniques for boron-aluminum composite-structure technology is presented and a new method of joining different laminated composites without mechanical fasteners is proposed. Also discussed is a low-cost procedure for rigidifying expanded honeycomb tubing and piping simulations. A brief note on patent information is added.

1976-01-01

34

Gradient composite materials for artificial intervertebral discs.  

PubMed

Composites with the gradient of Young's modulus constitute a new group of biomimetic materials which affect the proper distribution of stresses between the implant and the bone. The aim of this article was to examine the mechanical properties of gradient materials based on carbon fibre-polysulfone composite, and to compare them to the properties of a natural intervertebral disc. Gradient properties were provided by different orientation or volume fraction of carbon fibres in particular layers of composites. The results obtained during in vitro tests displayed a good durability of the gradient materials put under long-term static load. However, the configuration based on a change in the volume fraction of the fibres seems more advantageous than the one based on a change of the fibres' orientation. The materials under study were designed to replace the intervertebral disc. The effect of Young's modulus of the material layers on the stress distribution between the tissue and the implant was analyzed and the biomimetic character of the gradient composites was stated. Unlike gradient materials, the pure polysulfone and the non-gradient composite resulted in the stress concentration in the region of nucleus pulposus, which is highly disadvantageous and does not occur in the stress distribution of natural intervertebral discs. PMID:25306938

Migacz, Katarzyna; Ch?opek, Jan; Morawska-Chochó?, Anna; Ambroziak, Maciej

2014-01-01

35

Nanophase and Composite Optical Materials  

NASA Technical Reports Server (NTRS)

This talk will focus on accomplishments, current developments, and future directions of our work on composite optical materials for microgravity science and space exploration. This research spans the order parameter from quasi-fractal structures such as sol-gels and other aggregated or porous media, to statistically random cluster media such as metal colloids, to highly ordered materials such as layered media and photonic bandgap materials. The common focus is on flexible materials that can be used to produce composite or artificial materials with superior optical properties that could not be achieved with homogeneous materials. Applications of this work to NASA exploration goals such as terraforming, biosensors, solar sails, solar cells, and vehicle health monitoring, will be discussed.

2003-01-01

36

Carbon–Carbon Composite Materials  

Microsoft Academic Search

Data are summarized on the performance characteristics and properties of Russian-produced and foreign carbon–carbon composite materials for various engineering applications. The effect of neutron irradiation on their macroscopic properties and structure is examined. The relationships between the radiation-induced dimensional changes and properties of the composites are established, which can be used in assessing the engineering performance and optimizing the fabrication

Yu. S. Virgil'ev; I. P. Kalyagina

2004-01-01

37

Fracture problems in composite materials  

NASA Technical Reports Server (NTRS)

A series of fracture problems in composite materials are identified, their methods of solution are briefly discussed, and some sample results are presented. The main problem of interest is the determination of the stress state in the neighborhood of localized imperfections such as cracks and inclusions which may exist in the composite. Particular emphasis is placed on the evaluation of quantities such as the stress intensity factors, the power of the stress singularity, and the strain energy release rate, which may be used directly or indirectly in connection with an appropriate fracture criterion for the prediction of fracture initiation and propagation load levels. The topics discussed include a crack in layered composites, a crack terminating at and going through a bi-material interface, a penny-shaped crack in a filament-reinforced elastic matrix, and inclusion problems in bonded materials.

Erdogan, F.

1972-01-01

38

Pneumatic Characterization of Composite Materials  

Microsoft Academic Search

The dimensional change of some composite materials induced by ambient air pressure change was discovered and dubbed pneumatic strain in 2000. This pneumatic behavior closely resembles hygric behavior, and pneumatic strain is proportional to the ambient air pressure change by the coefficients of the pneumatic expansion. A method termed the suspension method was employed in this work to characterize the

Cho-Liang Tsai; Ming-Chang Cheng; Shun-Fa Hwang; Yi-Shiun Tsai

2002-01-01

39

Predicting Properties Of Composite Materials  

NASA Technical Reports Server (NTRS)

Micromechanical Combined Stress Analysis (MICSTRAN) computer code provides materials engineers with easy-to-use personal-computer-based software tool to calculate overall properties of composite, given properties of fibers and matrix. Computes overall thermoelastic parameters and stresses by micromechanical analysis. Written in FORTRAN 77.

Naik, Rajiv A.

1994-01-01

40

Pneumatic Behavior of Composite Materials  

Microsoft Academic Search

The dimensional change of some composite materials induced by ambient air pressure change was discovered and dubbed as pneumatic\\u000a strain in 2000. This pneumatic behavior is similar to the hygric behavior. The pneumatic strain is proportional to the ambient\\u000a air pressure change by the coefficients of pneumatic expansion. In this work, a technique termed suspending method was employed\\u000a for characterizing

Cho-Liang Tsai; Yi-Shiun Tsai

41

Aeroelastic tailoring of composite materials  

E-print Network

LIST OF FIGURES IiiTRODUCTI ON ST!!UCTURAL RESPONSE Deformation of Uniformly Stressed Isotropic and Anisotropic Plates Characterization of Composite Laminates . Effect of Material Parameters APPLICATIONS Aircraft Propellers Ship Propell rs... com- pliances with laminate rotation 39 15 Variation of (A) extensional ard (8) bending compliances with 0' ply rotation . . . . . . . . . . . . . . . . 40 16 Incremental aerodynamic forces on a typical blade element 43 17 Propeller velocity...

Rogers, Jesse Byron

2012-06-07

42

Improved Silica Aerogel Composite Materials  

NASA Technical Reports Server (NTRS)

A family of aerogel-matrix composite materials having thermal-stability and mechanical- integrity properties better than those of neat aerogels has been developed. Aerogels are known to be excellent thermal- and acoustic-insulation materials because of their molecular-scale porosity, but heretofore, the use of aerogels has been inhibited by two factors: (1) Their brittleness makes processing and handling difficult. (2) They shrink during production and shrink more when heated to high temperatures during use. The shrinkage and the consequent cracking make it difficult to use them to encapsulate objects in thermal-insulation materials. The underlying concept of aerogel-matrix composites is not new; the novelty of the present family of materials lies in formulations and processes that result in superior properties, which include (1) much less shrinkage during a supercritical-drying process employed in producing a typical aerogel, (2) much less shrinkage during exposure to high temperatures, and (3) as a result of the reduction in shrinkage, much less or even no cracking.

Paik, Jong-Ah; Sakamoto, Jeffrey; Jones, Steven

2008-01-01

43

Characterization of natural fiber surfaces and natural fiber composites  

Microsoft Academic Search

Experiments have been performed to further the development of natural fiber reinforced composites as a replacement for glass fiber composites. Untreated and treated surfaces of natural fibers were characterized using FTIR, XPS, and ESEM. Changes in the peaks in the FTIR spectrum at 1730, 1625 and 1239cm?1 indicated that the alkali treatment removes hemicellulose and lignin from natural fiber surfaces.

N. Sgriccia; M. C. Hawley; M. Misra

2008-01-01

44

Mechanical fastening of composite materials  

NASA Astrophysics Data System (ADS)

High-sensitivity moire interferometry was used to obtain the stress/strain distribution in the vicinity of mechanically fastened hole arrays in a glass/epoxy thermoset composite material. Experimental results are presented for three fastener configurations: the tandem configuration (two holes in a row parallel to the load direction), the parallel configuration (two fastening holes in a row perpendicular to the load direction), and the three-hole fastener array with all three holes equally loaded. The advantage of utilizing as multihole array in a connection rather than a single pin-loaded hole is demonstrated.

Zimmerman, K. B.

1992-08-01

45

http://jtc.sagepub.com Composite Materials  

E-print Network

http://jtc.sagepub.com Composite Materials Journal of Thermoplastic DOI: 10.1177/0892705708089473 2008; 21; 209Journal of Thermoplastic Composite Materials Qinglin Wu Sun-Young Lee, In-Aeh Kang, Geum://www.sagepublications.com at: can be foundJournal of Thermoplastic Composite MaterialsAdditional services and information

46

Properties of composite materials for cryogenic applications  

Microsoft Academic Search

Composite materials are used in a wide variety of cryogenic applications because of their unique and highly tailorable properties. These cryogenic applications of composites may be, for the sake of discussion, classified as support structures, vessels, or electrical insulation. Examples of these applications are presented, with a brief discussion of the critical material properties associated with each application. Composite material

J. B Schutz

1998-01-01

47

ULTRASONIC CHARACTERIZATION OF ADVANCED COMPOSITE MATERIALS  

Microsoft Academic Search

With increased use of composite materials in critical structural applications it is more important than ever to independently assure structural integrity. Complexity of the advanced composite materials including layered and bonded structures represents challenges in developing optimized ultrasonic tests. Traditional ultrasonic NDT methods are inappropriate and often misleading when applied to anisotropic and nonhomogeneous composite materials. In advanced technology applications

B. Boro Djordjevic

48

Composite materials for fusion applications  

SciTech Connect

Ceramic matrix composites, CMCs, are being considered for advanced first-wall and blanket structural applications because of their high-temperature properties, low neutron activation, low density and low coefficient of expansion coupled with good thermal conductivity and corrosion behavior. This paper presents a review and analysis of the hermetic, thermal conductivity, corrosion, crack growth and radiation damage properties of CMCs. It was concluded that the leak rates of a gaseous coolant into the plasma chamber or tritium out of the blanket could exceed design criteria if matrix microcracking causes existing porosity to become interconnected. Thermal conductivities of unirradiated SiC/SiC and C/SiC materials are about 1/2 to 2/3 that of Type 316 SS whereas the thermal conductivity for C/C composites is seven times larger. The thermal stress figure-of-merit value for CMCs exceeds that of Type 316 SS for a single thermal cycle. SiC/SiC composites are very resistant to corrosion and are expected to be compatible with He or Li coolants if the O{sub 2} concentrations are maintained at the appropriate levels. CMCs exhibit subcritical crack growth at elevated temperatures and the crack velocity is a function of the corrosion conditions. The radiation stability of CMCs will depend on the stability of the fiber, microcracking of the matrix, and the effects of gaseous transmutation products on properties. 23 refs., 14 figs., 1 tab.

Jones, R.H.; Henager, C.H. Jr.; Hollenberg, G.W.

1991-10-01

49

Nature of the ``Orange'' Material on Vesta from Dawn  

NASA Astrophysics Data System (ADS)

The Dawn mission revealed distinct units on Vesta with red spectral slope. Oppia ejecta is identified as “Leslie unit" postulated by Gaffey (1997). Orange material composition is unlikely to be metal or olivine. Its nature is most likely impact melt.

Le Corre, L.; Reddy, V.; Schmedemann, N.; Becker, K. J.; O'Brien, D. P.; Yamashita, N.; Peplowski, P. N.; Prettyman, T. H.; Li, J.-Y.; Cloutis, E. A.; Denevi, B. W.; Kneissl, T.; Palmer, E.; Gaskell, R. W.; Nathues, A.; Gaffey, M. J.; Mittlefehldt, D. W.; Gary, W. B.; Sierks, H.; Russell, C. T.; Raymond, C. A.

2014-02-01

50

Composite materials for thermal energy storage  

DOEpatents

The present invention discloses composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations. These phase change materials do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions, such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

Benson, David K. (Golden, CO); Burrows, Richard W. (Conifer, CO); Shinton, Yvonne D. (Northglenn, CO)

1986-01-01

51

Mechanics of interfacial composite materials.  

PubMed

Recent experiments and simulations have demonstrated that particle-covered fluid/fluid interfaces can exist in stable nonspherical shapes as a result of the steric jamming of the interfacially trapped particles. The jamming confers the interface with solidlike properties. We provide an experimental and theoretical characterization of the mechanical properties of these armored objects, with attention given to the two-dimensional granular state of the interface. Small inhomogeneous stresses produce a plastic response, while homogeneous stresses produce a weak elastic response. Shear-driven particle-scale rearrangements explain the basic threshold needed to obtain the near-perfect plastic deformation that is observed. Furthermore, the inhomogeneous stress state of the interface is exhibited experimentally by using surfactants to destabilize the particles on the surface. Since the interfacially trapped particles retain their individual characteristics, armored interfaces can be recognized as a kind of composite material with distinct chemical, structural, and mechanical properties. PMID:17107022

Subramaniam, Anand Bala; Abkarian, Manouk; Mahadevan, L; Stone, Howard A

2006-11-21

52

Strain rate behavior of composite materials  

Microsoft Academic Search

The effect of strain rate on the compressive and shear behavior of carbon\\/epoxy composite materials was investigated. Strain rate behavior of composites with fiber waviness was also studied. Falling weight impact system and servohydraulic testing machine were used for dynamic characterisation of composite materials in compression at strain rates up to several hundred per second. Strain rates below 10s?1 were

H. M. Hsiao; I. M. Daniel

1998-01-01

53

Polyolefin composites containing a phase change material  

DOEpatents

A composite useful in thermal energy storage, said composite being formed of a polyolefin matrix having a phase change material such as a crystalline alkyl hydrocarbon incorporated therein, said polyolefin being thermally form stable; the composite is useful in forming pellets, sheets or fibers having thermal energy storage characteristics; methods for forming the composite are also disclosed.

Salyer, Ival O. (Dayton, OH)

1991-01-01

54

Thin film dielectric composite materials  

DOEpatents

A dielectric composite material comprising at least two crystal phases of different components with TiO.sub.2 as a first component and a material selected from the group consisting of Ba.sub.1-x Sr.sub.x TiO.sub.3 where x is from 0.3 to 0.7, Pb.sub.1-x Ca.sub.x TiO.sub.3 where x is from 0.4 to 0.7, Sr.sub.1-x Pb.sub.x TiO.sub.3 where x is from 0.2 to 0.4, Ba.sub.1-x Cd.sub.x TiO.sub.3 where x is from 0.02 to 0.1, BaTi.sub.1-x Zr.sub.x O.sub.3 where x is from 0.2 to 0.3, BaTi.sub.1-x Sn.sub.x O.sub.3 where x is from 0.15 to 0.3, BaTi.sub.1-x Hf.sub.x O.sub.3 where x is from 0.24 to 0.3, Pb.sub.1-1.3x La.sub.x TiO.sub.3+0.2x where x is from 0.23 to 0.3, (BaTiO.sub.3).sub.x (PbFeo.sub.0.5 Nb.sub.0.5 O.sub.3).sub.1-x where x is from 0.75 to 0.9, (PbTiO.sub.3).sub.- (PbCo.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.1 to 0.45, (PbTiO.sub.3).sub.x (PbMg.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.2 to 0.4, and (PbTiO.sub.3).sub.x (PbFe.sub.0.5 Ta.sub.0.5 O.sub.3).sub.1-x where x is from 0 to 0.2, as the second component is described. The dielectric composite material can be formed as a thin film upon suitable substrates.

Jia, Quanxi (Los Alamos, NM); Gibbons, Brady J. (Los Alamos, NM); Findikoglu, Alp T. (Los Alamos, NM); Park, Bae Ho (Los Alamos, NM)

2002-01-01

55

Optimized adhesives for strong, lightweight, damage-resistant, nanocomposite materials: new insights from natural materials  

NASA Astrophysics Data System (ADS)

From our investigations of natural composite materials such as abalone shell and bone we have learned the following. (1) Nature is frugal with resources: it uses just a few per cent glue, by weight, to glue together composite materials. (2) Nature does not avoid voids. (3) Nature makes optimized glues with sacrificial bonds and hidden length. We discuss how optimized adhesives combined with high specific stiffness/strength structures such as carbon nanotubes or graphene sheets could yield remarkably strong, lightweight, and damage-resistant materials.

Hansma, P. K.; Turner, P. J.; Ruoff, R. S.

2007-01-01

56

Nonlinear Dynamic Properties of Layered Composite Materials  

SciTech Connect

We present an application of the asymptotic homogenization method to study wave propagation in a one-dimensional composite material consisting of a matrix material and coated inclusions. Physical nonlinearity is taken into account by considering the composite's components as a Murnaghan material, structural nonlinearity is caused by the bonding condition between the components.

Andrianov, Igor V.; Topol, Heiko; Weichert, Dieter [Institute of General Mechanics, RWTH Aachen University, Termplergraben 64, Aachen, D-52062 (Germany); Danishevs'kyy, Vladyslav V. [Prydniprovs'ka State Academy of Civil Engineering and Architecture, Dnipropetrovs'k, Chernishevs'kogo 24a, UA-49600 (Ukraine)

2010-09-30

57

A fatigue damage model of composite materials  

Microsoft Academic Search

The mechanical properties of composite materials degrade progressively with the increasing of the number of cyclic loadings. Based on the stiffness degradation rule of composites, a phenomenological fatigue damage model is presented in this paper, which contains two material parameters. They are proportional to the fatigue life of materials and inversely proportional to the fatigue loading level. Thirteen sets of

Fuqiang Wu; WeiXing Yao

2010-01-01

58

Mechanical Fasteners for Advanced Composite Materials  

NASA Technical Reports Server (NTRS)

Advanced composite materials, which are increasingly being used to build aircraft, have different properties than the metals they replace. Fasteners intended for composite-material joints must be designed and selected to allow for these differences. For example, blind fasteners (one-sided access) used to assemble composite-to-composite joints have been redesigned to expand to larger diameters to resist pull-through and cocking failures. The fastener designs needed for composite materials are reviewed. Topics discussed are: galvanic corrosion, pull-through resistance, fastener rotation, installation damage, fastener galling and conductivity. A blind fastener recently developed by SPS Technologies is described to show how these requirements are incorporated.

Landt, R. C.

1985-01-01

59

Method for machining holes in composite materials  

NASA Technical Reports Server (NTRS)

A method for boring well defined holes in a composite material such as graphite/epoxy is discussed. A slurry of silicon carbide powder and water is projected onto a work area of the composite material in which a hole is to be bored with a conventional drill bit. The silicon carbide powder and water slurry allow the drill bit, while experiencing only normal wear, to bore smooth, cylindrical holes in the composite material.

Daniels, Julia G. (inventor); Ledbetter, Frank E., III (inventor); Clemons, Johnny M. (inventor); Penn, Benjamin G. (inventor); White, William T. (inventor)

1987-01-01

60

Morphology and microstructure of composite materials  

NASA Technical Reports Server (NTRS)

Lightweight continuous carbon fiber based polymeric composites are currently enjoying increasing acceptance as structural materials capable of replacing metals and alloys in load bearing applications. As with most new materials, these composites are undergoing trials with several competing processing techniques aimed at cost effectively producing void free consolidations with good mechanical properties. As metallic materials have been in use for several centuries, a considerable database exists on their morphology - microstructure; and the interrelationships between structure and properties have been well documented. Numerous studies on composites have established the crucial relationship between microstructure - morphology and properties. The various microstructural and morphological features of composite materials, particularly those accompanying different processing routes, are documented.

Tiwari, S. N.; Srinivansan, K.

1991-01-01

61

Composite materials and method of making  

DOEpatents

A method for forming improved composite materials using a thermosetting polyester urethane hybrid resin, a closed cavity mold having an internal heat transfer mechanism used in this method, and the composite materials formed by this method having a hybrid of a carbon fiber layer and a fiberglass layer.

Simmons, Kevin L [Kennewick, WA; Wood, Geoffrey M [North Saanich, CA

2011-05-17

62

Composite materials for biomedical applications: a review.  

PubMed

The word "composite" refers to the combination, on a macroscopic scale, of two or more materials, different for composition, morphology and general physical properties. In many cases, and depending on the constituent properties, composites can be designed with a view to produce materials with properties tailored to fulfill specific chemical, physical or mechanical requirements. Therefore over the past 40 years the use of composites has progressively increased, and today composite materials have many different applications, i.e., aeronautic, automotive, naval, and so on. Consequently many composite biomaterials have recently been studied and tested for medical application. Some of them are currently commercialized for their advantages over traditional materials. Most human tissues such as bones, tendons, skin, ligaments, teeth, etc., are composites, made up of single constituents whose amount, distribution, morphology and properties determine the final behavior of the resulting tissue or organ. Man-made composites can, to some extent, be used to make prostheses able to mimic these biological tissues, to match their mechanical behavior and to restore the mechanical functions of the damaged tissue. Different types of composites that are already in use or are being investigated for various biomedical applications are presented in this paper. Specific advantages and critical issues of using composite biomaterials are also described (Journal of Applied Bio-materials & Biomechanics 2003; 1: 3-18). PMID:20803468

Salernitano, E; Migliaresi, C

2003-01-01

63

Flame-retardant composite materials  

NASA Technical Reports Server (NTRS)

The properties of eight different graphite composite panels fabricated using four different resin matrices and two types of graphite reinforcement are described. The resin matrices included: VPSP/BMI, a blend of vinylpolystyryl pyridine and bismaleimide; BMI, a bismaleimide; and phenolic and PSP, a polystyryl pyridine. The graphite fiber used was AS-4 in the form of either tape or fabric. The properties of these composites were compared with epoxy composites. It was determined that VPSP/BMI with the graphite tape was the optimum design giving the lowest heat release rate.

Kourtides, Demetrius A.

1991-01-01

64

Fourth Symposium on Composite Materials  

Microsoft Academic Search

The high temperature fatigue of a (O)12 tungsten fiber reinforced copper matrix composite was investigated. Specimens having fiber volume percentages of 10 and 36 were fatigued under fully-reversed, strain-controlled conditions at both 260 and 560 C. The fatigue life was found to be independent of fiber volume fraction because fatigue damage preferentially occurred in the matrix. Also, the composite fatigue

M. J. Verrilli; T. P. Gabb

1990-01-01

65

New textile composite materials development, production, application  

NASA Technical Reports Server (NTRS)

New textile composite materials development, production, and application are discussed. Topics covered include: super-high-strength, super-high-modulus fibers, filaments, and materials manufactured on their basis; heat-resistant and nonflammable fibers, filaments, and textile fabrics; fibers and textile fabrics based on fluorocarbon poylmers; antifriction textile fabrics based on polyfen filaments; development of new types of textile combines and composite materials; and carbon filament-based fabrics.

Mikhailov, Petr Y.

1993-01-01

66

Load-bearing natural fiber composite cellular beams and panels  

Microsoft Academic Search

Natural fiber composites, or biocomposites, have recently gained much attention due to their low cost, environmental friendliness, and their potential to compete with glass-fiber composites. The reported study demonstrates that biocomposites can be used for load-bearing components by improving their structural efficiency through cellular material arrangements. Laboratory-scale periodic cellular beams and plates were made from industrial hemp and flax fibers

Rigoberto Burgueño; Mario J. Quagliata; Amar K. Mohanty; Geeta Mehta; Lawrence T. Drzal; Manjusri Misra

2004-01-01

67

Combinatorial synthesis of inorganic or composite materials  

DOEpatents

Methods and apparatus for the preparation and use of a substrate having an array of diverse materials in predefined regions thereon. A substrate having an array of diverse materials thereon is generally prepared by delivering components of materials to predefined regions on a substrate, and simultaneously reacting the components to form at least two materials or, alternatively, allowing the components to interact to form at least two different materials. Materials which can be prepared using the methods and apparatus of the present invention include, for example, covalent network solids, ionic solids and molecular solids. More particularly, materials which can be prepared using the methods and apparatus of the present invention include, for example, inorganic materials, intermetallic materials, metal alloys, ceramic materials, organic materials, organometallic materials, nonbiological organic polymers, composite materials (e.g., inorganic composites, organic composites, or combinations thereof), etc. Once prepared, these materials can be screened for useful properties including, for example, electrical, thermal, mechanical, morphological, optical, magnetic, chemical, or other properties. Thus, the present invention provides methods for the parallel synthesis and analysis of novel materials having useful properties.

Goldwasser, Isy (Palo Alto, CA); Ross, Debra A. (Mountain Ranch, CA); Schultz, Peter G. (La Jolla, CA); Xiang, Xiao-Dong (Danville, CA); Briceno, Gabriel (Baldwin Park, CA); Sun, Xian-Dong (Fremont, CA); Wang, Kai-An (Cupertino, CA)

2010-08-03

68

Materials research at Stanford University. [composite materials, crystal structure, acoustics  

NASA Technical Reports Server (NTRS)

Research activity related to the science of materials is described. The following areas are included: elastic and thermal properties of composite materials, acoustic waves and devices, amorphous materials, crystal structure, synthesis of metal-metal bonds, interactions of solids with solutions, electrochemistry, fatigue damage, superconductivity and molecular physics and phase transition kinetics.

1975-01-01

69

An engineering point of view about fatigue of polymer matrix composite materials  

Microsoft Academic Search

High performance polymer composite materials reinforced by long fibres have a reputation for good fatigue behaviour. Let us note, in connection with the above statement, that the substitution of metals by composite materials is a success for aeronautical applications. However, fatigue of composite materials is still an important problem for an engineering point of view, because its nature is basically

Claude Bathias

2006-01-01

70

Oxygen Compatibility Testing of Composite Materials  

NASA Technical Reports Server (NTRS)

Composite materials offer significant weight-saving potential for aerospace applications in propellant and oxidizer tanks. This application for oxygen tanks presents the challenge of being oxygen compatible in addition to complying with the other required material characteristics. This effort reports on the testing procedures and data obtained in examining and selecting potential composite materials for oxygen tank usage. Impact testing of composites has shown that most of these materials initiate a combustion event when impacted at 72 ft-lbf in the presence of liquid oxygen, though testing has also shown substantial variability in reaction sensitivities to impact. Data for screening of 14 potential composites using the Bruceton method is given herein and shows that the 50-percent reaction frequencies range from 17 to 67 ft-lbf. The pressure and temperature rises for several composite materials were recorded to compare the energy releases as functions of the combustion reactions with their respective reaction probabilities. The test data presented are primarily for a test pressure of 300 psia in liquid oxygen. The impact screening process is compared with oxygen index and autogenous ignition test data for both the composite and the basic resin. The usefulness of these supplemental tests in helping select the most oxygen compatible materials is explored. The propensity for mechanical impact ignition of the composite compared with the resin alone is also examined. Since an ignition-free composite material at the peak impact energy of 72 ft-lbf has not been identified, composite reactivity must be characterized over the impact energy level and operating pressure ranges to provide data for hazard analyses in selecting the best potential material for liquid tank usage.

Engel, Carl D.; Watkins, Casey N.

2006-01-01

71

Multiscale Modeling and Homogenization of Composite Materials  

E-print Network

of composites that account for the micro-structuralpertinent micro-structural infor- mation. For compositecomposite materials is to use the finite element method. In particular, since accounting for all the micro-

Mseis, George

2010-01-01

72

Reliability and micromechanics of composite materials  

Microsoft Academic Search

A methodology is proposed to evaluate the reliability of composites. Micromechanical analysis is utilized as a basis for the representation of the effects of constituent properties on global response. The analysis is then combined with the models of structural reliability to study the influence of micro-level material parameters on reliability of composites under static loadings.

Zhanjun Gao

1992-01-01

73

Composite Materials for Wind Power Turbine Blades  

Microsoft Academic Search

Renewable energy resources, of which wind energy is prominent, are part of the solution to the global energy problem. Wind turbine and the rotorblade concepts are reviewed, and loadings by wind and gravity as important factors for the fatigue performance of the materials are considered. Wood and composites are discussed as candidates for rotorblades. The fibers and matrices for composites

Povl Brøndsted; Hans Lilholt; Aage Lystrup

2005-01-01

74

Composite materials inspection. [ultrasonic vibration holographic NDT  

NASA Technical Reports Server (NTRS)

Investigation of the application requirements, advantages, and limitations of nondestructive testing by a technique of ultrasonic-vibration holographic-interferometry readout used in a production control facility for the inspection of a single product such as composite compressor blades. It is shown that, for the detection and characterization of disbonds in composite material structures, this technique may represent the most inclusive test method.

Erf, R. K.

1974-01-01

75

Candida albicans adhesion to composite resin materials  

Microsoft Academic Search

The adhesion of Candida albicans to dental restorative materials in the human oral cavity may promote the occurrence of oral candidosis. This study aimed\\u000a to compare the susceptibility of 14 commonly used composite resin materials (two compomers, one ormocer, one novel silorane,\\u000a and ten conventional hybrid composites) to adhere Candida albicans. Differences in the amount of adhering fungi should be

Ralf Bürgers; Wulf Schneider-Brachert; Martin Rosentritt; Gerhard Handel; Sebastian Hahnel

2009-01-01

76

Method to fabricate layered material compositions  

DOEpatents

A new class of processes suited to the fabrication of layered material compositions is disclosed. Layered material compositions are typically three-dimensional structures which can be decomposed into a stack of structured layers. The best known examples are the photonic lattices. The present invention combines the characteristic features of photolithography and chemical-mechanical polishing to permit the direct and facile fabrication of, e.g., photonic lattices having photonic bandgaps in the 0.1-20.mu. spectral range.

Fleming, James G. (Albuquerque, NM); Lin, Shawn-Yu (Albuquerque, NM)

2002-01-01

77

Acoustic emission monitoring of polymer composite materials  

NASA Technical Reports Server (NTRS)

The techniques of acoustic emission monitoring of polymer composite materials is described. It is highly sensitive, quasi-nondestructive testing method that indicates the origin and behavior of flaws in such materials when submitted to different load exposures. With the use of sophisticated signal analysis methods it is possible the distinguish between different types of failure mechanisms, such as fiber fracture delamination or fiber pull-out. Imperfections can be detected while monitoring complex composite structures by acoustic emission measurements.

Bardenheier, R.

1981-01-01

78

Method of making a composite refractory material  

DOEpatents

A composite refractory material is prepared by combining boron carbide with furan resin to form a mixture containing about 8 wt. % furan resin. The mixture is formed into a pellet which is placed into a grit pack comprising an oxide of an element such as yttrium to form a sinterable body. The sinterable body is sintered under vacuum with microwave energy at a temperature no greater than 2000.degree. C. to form a composite refractory material.

Morrow, Marvin S. (Kingston, TN); Holcombe, Cressie E. (Knoxville, TN)

1995-01-01

79

Fatigue and fracture research in composite materials  

NASA Technical Reports Server (NTRS)

The fatigue, fracture, and impact behavior of composite materials are investigated. Bolted and bonded joints are included. The solutions developed are generic in scope and are useful for a wide variety of structural applications. The analytical tools developed are used to demonstrate the damage tolerance, impact resistance, and useful fatigue life of structural composite components. Standard tests for screening improvements in materials and constituents are developed.

Obrien, T. K.

1982-01-01

80

Oxygen isotope composition of trinitite postdetonation materials.  

PubMed

Trinitite is the melt glass produced subsequent the first nuclear bomb test conducted on July 16, 1945, at White Sands Range (Alamagordo, NM). The geological background of the latter consists of arkosic sand that was fused with radioactive debris and anthropogenic materials at ground zero subsequent detonation of the device. Postdetonation materials from historic nuclear weapon test sites provide ideal samples for development of novel forensic methods for attribution and studying the chemical/isotopic effects of the explosion on the natural geological environment. In particular, the latter effects can be evaluated relative to their spatial distribution from ground zero. We report here ?(18)O(‰) values for nonmelted, precursor minerals phases (quartz, feldspar, calcite), "feldspathic-rich" glass, "average" melt glass, and bulk (natural) unmelted sand from the Trinity site. Prior to oxygen isotope analysis, grains/crystals were examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to determine their corresponding major element composition. ?(18)O values for bulk trinitite samples exhibit a large range (11.2-15.5‰) and do not correlate with activity levels for activation product (152)Eu; the latter levels are a function of their spatial distribution relative to ground zero. Therefore, the slow neutron flux associated with the nuclear explosion did not perturb the (18)O/(16)O isotope systematics. The oxygen isotope values do correlate with the abundances of major elements derived from precursor minerals present within the arkosic sand. Hence, the O isotope ratios documented here for trinitite melt glass can be attributed to a mixture of the respective signatures for precursor minerals at the Trinity site prior to the nuclear explosion. PMID:24304329

Koeman, Elizabeth C; Simonetti, Antonio; Chen, Wei; Burns, Peter C

2013-12-17

81

Offgassing test methodology for composite materials  

NASA Technical Reports Server (NTRS)

A significant increase in the use of composite materials has occurred during the past 20 years. Associated with this increased use is the potential for employees to be exposed to offgassing components from composite systems. Various components in composite systems, particularly residual solvents, offgas under various conditions. The potential for offgassing to occur increases as a composite material is heated either during cure or during lay-up operations. Various techniques can be employed to evaluate the offgassing characteristics of a composite system. A joint effort between AIA and SACMA resulted in the drafting of a proposed test method for evaluating the offgassing potential of composite materials. The purpose of testing composite materials for offgassing is to provide the industrial hygienist with information which can be used to assess the safety of the workplace. This paper outlines the proposed test method and presents round robin testing data associated with the test method. Also in this presentation is a discussion of classes of compounds which require specialized sampling techniques.

Scheer, Dale A.

1994-01-01

82

Compositional gradients in natural silicic liquids  

SciTech Connect

Electron microprobe analyses of natural rhyolite glass reveal compositional gradients 10 to 15 ..mu..m wide adjacent to microphenocrysts of plagioclase, alkali feldspar, and magnetite. The presence of such gradients has previously been interpreted as indicative of disequilibrium between liquid and solid. If crystals and liquid are not in compositional equilibrium, temperatures determined from the compositions of coexisting mineral phases might be erroneous. Gradients may be attributed, however, to diffusion controlled crystallization. Because convection of magma is indicated based on a comparison of characteristic transport distances and thickness of compositional boundary layers the model of Tiller et al. (1953) is deemed inappropriate. The microprobe data are consistent with the model of Burton, Prim, and Slichter (1953) in which the liquid is stirred by convection and the crystals are surrounded by a diffusive-advective boundary layer. Computed apparent and equilibrium distribution coefficients for natural rhyolites, combined with published diffusion coefficients for K, yield linear growth rates for feldspars on the order of 7 x 10/sup -7/ cm sec/sup -1/, similar to experimentally determined equilibrium growth rates. The analytical data are consistent with a model of diffusion controlled crystallization in natural silicic liquids, and the utilization of coexisting phases for thermometry remains reasonable in the presence of narrow compositional gradients.

Evans, S.H. Jr.: Nash, W.P.

1980-09-01

83

3-D textile reinforcements in composite materials  

SciTech Connect

Laminated composite materials have been used in structural applications since the 1960s. However, their high cost and inability to accommodate fibers in the laminate`s thickness direction greatly reduce their damage tolerance and impact resistance. The second generation of materials--3-D textile reinforced composites--offers significant cost reduction, and by incorporating reinforcement in the thickness direction, dramatically increases damage tolerance and impact resistance. However, methods for predicting mechanical properties of 3-D textile reinforced composite materials tend to be more complex. These materials also have disadvantages--particularly in regard to crimps in the yarns--that require more research. Textile preforms, micro- and macromechanical modeling, manufacturing processes, and characterization all need further development. As researchers overcome these problems, this new generation of composites will emerge as a highly competitive family of materials. This book provides a state-of-the-art account of this promising technology. In it, top experts describe the manufacturing processes, highlight the advantages, identify the main applications, analyze methods for predicting mechanical properties, and detail various reinforcement strategies, including grid structure, knitted fabric composites, and the braiding technique. Armed with the information in this book, readers will be prepared to better exploit the advantages of 3-D textile reinforced composites, overcome its disadvantages, and contribute to the further development of the technology.

Miravete, A. [Univ. of Zaragoza (Spain)

1999-11-01

84

Micromechanics of composite materials under compressive loading  

Microsoft Academic Search

A common thread joining many engineered materials used dominantly under compressive loading is the presence of a high modulus secondary phase, either fiber or particulate, embedded within a lower modulus matrix phase. To improve their toughness, a frictional or a less-than-coherent interface is strived for in the manufacture of these composite materials. To form a better understanding of the complex

G. Laird; T. C. Kennedy

1995-01-01

85

ADVANCED COMPOSITE MATERIALS FOR BRIDGES Sami RIZKALLA  

E-print Network

1. SUMMARY ADVANCED COMPOSITE MATERIALS FOR BRIDGES Sami RIZKALLA ISIS Canada Network of Centres bridges are being built with materials that have significantly higher strength in comparison to steel associated with concrete bridges due to the corrosion of steel reinforcements. This paper presents

86

Composite Materials for Wind Power Turbine Blades  

NASA Astrophysics Data System (ADS)

Renewable energy resources, of which wind energy is prominent, are part of the solution to the global energy problem. Wind turbine and the rotorblade concepts are reviewed, and loadings by wind and gravity as important factors for the fatigue performance of the materials are considered. Wood and composites are discussed as candidates for rotorblades. The fibers and matrices for composites are described, and their high stiffness, low density, and good fatigue performance are emphasized. Manufacturing technologies for composites are presented and evaluated with respect to advantages, problems, and industrial potential. The important technologies of today are prepreg (pre-impregnated) technology and resin infusion technology. The mechanical properties of fiber composite materials are discussed, with a focus on fatigue performance. Damage and materials degradation during fatigue are described. Testing procedures for documentation of properties are reviewed, and fatigue loading histories are discussed, together with methods for data handling and statistical analysis of (large) amounts of test data. Future challenges for materials in the field of wind turbines are presented, with a focus on thermoplastic composites, new structural materials concepts, new structural design aspects, structural health monitoring, and the coming trends and markets for wind energy.

Brøndsted, Povl; Lilholt, Hans; Lystrup, Aage

2005-08-01

87

Fungal-modification of Natural Fibers: A Novel Method of Treating Natural Fibers for Composite Reinforcement  

Microsoft Academic Search

Growing interest in green products has provided fresh impetus to the research in the field of renewable materials. Plant fibers are not only renewable but also light in weight and low in cost. Polymer composites manufactured using them find applications in diverse fields such as automobiles, housing, and furniture. However, their hydrophilic nature and inadequate adhesion with matrix limits their

Deepaksh Gulati; Mohini Sain

2006-01-01

88

New demands on manufacturing of composite materials  

SciTech Connect

Traditionally the field of advanced composites has been dominated by the needs of the aerospace industry. This has strongly influenced the materials and processes developed. However, during the last few years, a shift of emphasis into other engineering areas has been obvious. Branches such as the mechanical industry, ground transportation, the building industry and the leisure industry are today defining many of the new areas of application for these materials. In these applications fiber-reinforced composites are not just used in large structures but also in crucial small complex-shaped elements of larger machinery in order to improve overall performance. To satisfy these new demands, it is essential to develop innovative material systems and processing techniques which enable the production of composite parts with complex geometries at reasonable cost and with high precision. Most likely the solution to this task lies in the closely integrated development of the material system and the manufacturing method. Several different approaches are today taken in order to reach this goal for composite materials. Furthermore, it is nowadays important that the introduction of any new material or application, especially for high volume production, be accompanied by a thorough life-cycle and environmental plan.

Manson, J.A.E. [Ecole Polytechnique Federale de Lausanne (Switzerland). Lab. de Technologie des Composites et Polymeres

1994-12-31

89

Introduction: Atomistic Nature of Materials  

NASA Astrophysics Data System (ADS)

Materials are made of atoms. The atomic hypothesis was put forward by the Greek philosopher Demokritos about 25 centuries ago, but was only proven by quantitative arguments in the 19th and 20th centuries, beginning with the work of John Dalton (1766-1844) and through the development of quantum mechanics, the theory that provided a complete and accurate description of the properties of atoms. The very large number of atoms encountered in a typical material (of order ˜1024or more) precludes any meaningful description of its properties based on a complete account of the behavior of each and every atom that comprises it. Special cases, such as perfect crystals, are exceptions where symmetry reduces the number of independent atoms to very few; in such cases, the properties of the solid are indeed describable in terms of the behavior of the few independent atoms and this can be accomplished using quantum mechanical methods. However, this is only an idealized model of actual solids in which perfect order is broken either by thermal disorder or by the presence of defects that play a crucial role in determining the physical properties of the system.

Kaxiras, Efthimios; Yip, Sidney

90

Impact testing of textile composite materials  

NASA Technical Reports Server (NTRS)

The objectives of this report were to evaluate the impact damage resistance and damage tolerance of a variety of textile composite materials. Static indentation and impact tests were performed on the stitched and unstitched uniweave composites constructed from AS4/3501-6 Carbon/Epoxy with a fiberglass yarn woven in to hold the fibers together while being stitched. Compression and tension were measured after the tests to determine the damage resistance, residual strength and the damage tolerance of the specimens.

Portanova, Marc

1995-01-01

91

Chemistry and technology of radiation processed composite materials  

NASA Astrophysics Data System (ADS)

Composite materials of synthetics (based on monomers, oligomers and thermoplastics) and of natural polymers (wood and other fibrous cellulosics) prepared by radiation processing, offer valuable structural materials with enhanced coupling forces between the components. The applied polymer chemistry of such composites shows several common features with that of radiation grafting. E.g. the polymerization rate of oligomer-monomer mixtures in wood remains in most cases proportional to the square-root of the initiating dose-rate, just as in the simultaneous grafting, demonstrating that the chain termination kinetics remain regularly bimolecular in the corresponding dose-rate ranges. In the processing experiences of such composites, low dose requirement, easy process-control, and good technical feasibility have been found for composites of wood with oligomer-monomer mixtures, for coconut fibres with unsaturated polyesters and for pretreated wood fibre with polypropylene.

Czvikovszky, T.

92

Computational modeling of composite material fires.  

SciTech Connect

Composite materials behave differently from conventional fuel sources and have the potential to smolder and burn for extended time periods. As the amount of composite materials on modern aircraft continues to increase, understanding the response of composites in fire environments becomes increasingly important. An effort is ongoing to enhance the capability to simulate composite material response in fires including the decomposition of the composite and the interaction with a fire. To adequately model composite material in a fire, two physical model development tasks are necessary; first, the decomposition model for the composite material and second, the interaction with a fire. A porous media approach for the decomposition model including a time dependent formulation with the effects of heat, mass, species, and momentum transfer of the porous solid and gas phase is being implemented in an engineering code, ARIA. ARIA is a Sandia National Laboratories multiphysics code including a range of capabilities such as incompressible Navier-Stokes equations, energy transport equations, species transport equations, non-Newtonian fluid rheology, linear elastic solid mechanics, and electro-statics. To simulate the fire, FUEGO, also a Sandia National Laboratories code, is coupled to ARIA. FUEGO represents the turbulent, buoyantly driven incompressible flow, heat transfer, mass transfer, and combustion. FUEGO and ARIA are uniquely able to solve this problem because they were designed using a common architecture (SIERRA) that enhances multiphysics coupling and both codes are capable of massively parallel calculations, enhancing performance. The decomposition reaction model is developed from small scale experimental data including thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) in both nitrogen and air for a range of heating rates and from available data in the literature. The response of the composite material subject to a radiant heat flux boundary condition is examined to study the propagation of decomposition fronts of the epoxy and carbon fiber and their dependence on the ambient conditions such as oxygen concentration, surface flow velocity, and radiant heat flux. In addition to the computational effort, small scaled experimental efforts to attain adequate data used to validate model predictions is ongoing. The goal of this paper is to demonstrate the progress of the capability for a typical composite material and emphasize the path forward.

Brown, Alexander L.; Erickson, Kenneth L.; Hubbard, Joshua Allen; Dodd, Amanda B.

2010-10-01

93

A physically-based abrasive wear model for composite materials  

SciTech Connect

A simple physically-based model for the abrasive wear of composite materials is presented based on the mechanics and mechanisms associated with sliding wear in soft (ductile) matrix composites containing hard (brittle) reinforcement particles. The model is based on the assumption that any portion of the reinforcement that is removed as wear debris cannot contribute to the wear resistance of the matrix material. The size of this non-contributing portion of the reinforcement is estimated by modeling the three primary wear mechanisms, specifically plowing, interfacial cracking and particle removal. Critical variables describing the role of the reinforcement, such as its relative size and the nature of the matrix/reinforcement interface, are characterized by a single contribution coefficient, C. Predictions are compared with the results of experimental two-body (pin-on drum) abrasive wear tests performed on a model aluminum particulate-reinforced epoxy matrix composite material.

Lee, Gun Y.; Dharan, C.K.H.; Ritchie, Robert O.

2001-05-01

94

Carbon storage potential in natural fiber composites  

Microsoft Academic Search

The environmental performance of hemp based natural fiber mat thermoplastic (NMT) has been evaluated in this study by quantifying carbon storage potential and CO2 emissions and comparing the results with commercially available glass fiber composites. Non-woven mats of hemp fiber and polypropylene matrix were used to make NMT samples by film-stacking method without using any binder aid. The results showed

Muhammad Pervaiz; Mohini M Sain

2003-01-01

95

Testing of NCSX Composite Coil Material Properties  

SciTech Connect

The National Compact Stellarator Experiment (NCSX) is now in design and requires 18 modular coils that are constructed to a highly complex geometry. The modular coil conductors are designed as a composite of a fine gauge stranded copper cable shaped to the required geometry and vacuum impregnated with a resin. These composite conductors exhibit unique material properties that must be determined and verified through testing. The conductor material properties are necessary for design modeling and performance validation. This paper will present the methods used to test and measure the coil conductor material properties, the unique challenges in measuring these complex materials at both room and liquid nitrogen temperatures and the results of those tests.

Kozub, Thomas; Jurczynski, Stephan; Chrzanowski, James [Princeton Plasma Physics Laboratory (United States)

2005-05-15

96

Ground exposure of composite materials for helicopters  

NASA Technical Reports Server (NTRS)

Residual strength results are presented on four composite material systems that were exposed for three years at locations on the North American Continent. The exposure locations are near the areas where Bell Model 206L Helicopters, that are in a NSA/U.S. Army sponsored flight service program, are flying in daily commercial service. The composite systems are: (1) Kevlar-49 fabric/F-185 epoxy; (2) Kevlar-49 fabric/LRF-277 epoxy; (3) Kevlar-49 fabric/CE-306 epoxy; and (4) T-300 Graphite/E-788 epoxy. All material systems exhibited good strength retention in compression and short beam shear. The Kevlar-49/LRF-277 epoxy retained 88 to 93 percent of the baseline strength while the other material systems exceeded 95 percent of baseline strength. Residual tensile strength of all materials did not show a significant reduction. The available moisture absorption data is also presented.

Baker, D. J.

1984-01-01

97

Composite materials for rail transit systems  

NASA Technical Reports Server (NTRS)

The potential is explored for using composite materials in urban mass transit systems. The emphasis was to identify specific advantages of composite materials in order to determine their actual and potential usage for carbody and guideway structure applications. The literature was reviewed, contacts were made with major domestic system operators, designers, and builders, and an analysis was made of potential composite application to railcar construction. Composites were found to be in use throughout the transit industry, usually in secondary or auxiliary applications such as car interior and nonstructural exterior panels. More recently, considerable activity has been initiated in the area of using composites in the load bearing elements of civil engineering structures such as highway bridges. It is believed that new and improved manufacturing refinements in pultrusion and filament winding will permit the production of beam sections which can be used in guideway structures. The inherent corrosion resistance and low maintenance characteristics of composites should result in lowered maintenance costs over a prolonged life of the structure.

Griffin, O. Hayden, Jr.; Guerdal, Zafer; Herakovich, Carl T.

1987-01-01

98

Composite materials in flexible multibody systems  

Microsoft Academic Search

In this work the flexible multibody dynamics formulations of complex models are extended to include elastic components made of laminated composite materials. The only limitation for the deformation of a structural member is that it must be elastic and linear when described in a body fixed frame. A finite element model for each flexible body is obtained such that the

Maria Augusta Neto; Jorge A. C. Ambrósio; Rogério P. Leal

2006-01-01

99

MECHANICS METHODOLOGY FOR TEXTILE PREFORM COMPOSITE MATERIALS  

Microsoft Academic Search

NASA and its contractors have completed a program to develop a basic mechanics underpinning for textile composites. Three major deliverables were produced by the program: 1. a set of test methods for measuring material properties and design allowables 2. mechanics models to predict the effects of the fiber preform architecture and constituent properties on engineering moduli, strength, damage resistance, and

Clarence C. Poe

1996-01-01

100

Data-mined similarity function between material compositions  

E-print Network

A new method for assessing the similarity of material compositions is described. A similarity measure is important for the classification and clustering of compositions. The similarity of the material compositions is ...

Yang, Lusann

101

Autophagous spacecraft composite materials for orbital propulsion  

NASA Astrophysics Data System (ADS)

We are developing structural polymer composite materials that can be converted into fuels and combusted with oxidizers for orbital propulsion of spacecraft. We have identified candidate materials and demonstrated sustained combustion with nitrogen tetroxide (NTO) as an oxidizer. To improve reaction chemistry we have evaluated several energetic additives. Detailed material compatibility tests were conducted to identify stable combinations of structural polymer and energetic additives. We have also demonstrated sustained combustion of structural polymeric materials with embedded additives and NTO. In the next phase of research, we plan to investigate hydrogen peroxide as the oxidizer. Samples of composites comprising thin metallic facesheets, structural polymer propellant matrix, and metallic mesh reinforcements (that also serve as electrical heaters/igniters for pyrolysis) were fabricated and their mechanical properties were measured. Concept of a spacecraft structural stringer, which also functions as a thruster, was developed using the composite material formulation. Both all solid and hybrid stringer-thruster designs have been developed. Prototype stringer-thrusters will be fabricated and tested in Phase II.

Joshi, Prakash; Upschulte, Bernard L.; Gelb, Alan H.; Green, B. David; Lester, Dean M.; Wallace, Ingvar; Starrett, W. David; Marshall, David W.

2002-07-01

102

Accelerated Aging of Polymer Composite Bridge Materials  

SciTech Connect

Accelerated aging research on samples of composite material and candidate ultraviolet (UV) protective coatings is determining the effects of six environmental factors on material durability. Candidate fastener materials are being evaluated to determine corrosion rates and crevice corrosion effects at load-bearing joints. This work supports field testing of a 30-ft long, 18-ft wide polymer matrix composite (PMC) bridge at the Idaho National Engineering and Environmental Laboratory (INEEL). Durability results and sensor data from tests with live loads provide information required for determining the cost/benefit measures to use in life-cycle planning, determining a maintenance strategy, establishing applicable inspection techniques, and establishing guidelines, standards, and acceptance criteria for PMC bridges for use in the transportation infrastructure.

J. G. Rodriguez; L. G. Blackwood; L. L. Torres; N. M. Carlson; T. S. Yoder

1999-03-01

103

Fungal degradation of fiber-reinforced composite materials  

NASA Technical Reports Server (NTRS)

As described in a previous report, a fungal consortium isolated from degraded polymeric materials was capable of growth on presterilized coupons of five composites, resulting in deep penetration into the interior of all materials within five weeks. Data describing the utilization of composite constituents as nutrients for the microflora are described in this article. Increased microbial growth was observed when composite extract was incubated with the fungal inoculum at ambient temperatures. Scanning electron microscopic observation of carbon fibers incubated with a naturally developed population of microorganisms showed the formation of bacterial biofilms on the fiber surfaces, suggesting possible utilization of the fiber chemical sizing as carbon and energy sources. Electrochemical impedance spectroscopy was used to monitor the phenomena occurring at the fiber-matrix interfaces. Significant differences were observed between inoculated and sterile panels of the composite materials. A progressive decline in impedance was detected in the inoculated panels. Several reaction steps may be involved in the degradation process. Initial ingress of water into the resin matrix appeared to be followed by degradation of fiber surfaces, and separation of fibers from the resin matrix. This investigation suggested that composite materials are susceptible to microbial attack by providing nutrients for growth.

Gu, J. D.; Lu, C.; Mitchell, R.; Thorp, K.; Crasto, A.

1997-01-01

104

Composite materials for precision space reflector panels  

NASA Technical Reports Server (NTRS)

One of the critical technology needs of large precision reflectors for future astrophysical and optical communications satellites lies in the area of structural materials. Results from a materials research and development program at NASA Langley Research Center to provide materials for these reflector applications are discussed. Advanced materials that meet the reflector panel requirements are identified, and thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared. A parabolic, graphite-phenolic honeycomb composite panel having a surface accuracy of 70.8 microinches rms and an areal weight of 1.17 lbm/sq ft was fabricated with T50/ERL1962 facesheets, a PAEI thermoplastic surface film, and Al and SiO(x) coatings.

Tompkins, Stephen S.; Funk, Joan G.; Bowles, David E.; Towell, Timothy W.; Connell, John W.

1992-01-01

105

Mechanics of failure of composite materials  

NASA Technical Reports Server (NTRS)

Composite materials are both inhomogeneous and anisotropic. Both of these characteristics affect the internal stress distributions since inhomogeneity involves variations in both strength and stiffness. The fracture mechanics of nonuniform materials are considered, taking into account the effect of nonuniformity on stress distributions near the crack tip, predicted yield zones in nonuniform and uniform materials, and the fracture of a center-notched unidirectional specimen. The mechanics of failure of laminated materials is discussed. It is found that the development of damage in a laminate with increasing load and, possibly, increasing numbers of cycles of loading is peculiar to the laminate in question, i.e., the material system, the stacking sequence, and the geometry. Approaches for monitoring damage development are also described.

Reifsnider, K. L.

1978-01-01

106

Mishap risk control for advanced aerospace/composite materials  

NASA Technical Reports Server (NTRS)

Although advanced aerospace materials and advanced composites provide outstanding performance, they also present several unique post-mishap environmental, safety, and health concerns. The purpose of this paper is to provide information on some of the unique hazards and concerns associated with these materials when damaged by fire, explosion, or high-energy impact. Additionally, recommended procedures and precautions are addressed as they pertain to all phases of a composite aircraft mishap response, including fire-fighting, investigation, recovery, clean-up, and guidelines are general in nature and not application-specific. The goal of this project is to provide factual and realistic information which can be used to develop consistent and effective procedures and policies to minimize the potential environmental, safety, and health impacts of a composite aircraft mishap response effort.

Olson, John M.

1994-01-01

107

New Discovery in the Properties of Composites Reinforced with Natural Fibers  

Microsoft Academic Search

Composite materials with thermoplastic matrices and a reinforcement of natural fibers are increasingly regarded as an alternative to glass fiber-reinforced composites. The substitution of the traditionally used reinforcing glass fibers by natural fibers such as flax, kenaf, or cotton can lead to a reduction of the component’s weight and furthermore to a significant improvement of specific properties like impact strength,

Dieter H. Mueller; Andreas Krobjilowski

2003-01-01

108

Fracture mechanics for delamination problems in composite materials  

NASA Technical Reports Server (NTRS)

A fracture mechanics approach to the well-known delamination problem in composite materials is presented. Based on the theory of anisotropic laminate elasticity and interlaminar fracture mechanics concepts, the composite delamination problem is formulated and solved. The exact order of the delamination crack-tip stress singularity is determined. Asymptotic stress and displacement fields for an interlaminar crack are obtained. Fracture mechanics parameters such as mixed-mode stress intensity factors, KI, KII, KIII, and the energy release rate, G, for composite delamination problems are defined. To illustrate the fundamental nature of the delamination crack behavior, solutions for edge-delaminated graphite-epoxy composites under uniform axial extension are presented. Effects of fiber orientation, ply thickness, and delamination length on the interlaminar fracture are examined.

Wang, S. S.

1983-01-01

109

Compression Testing of Textile Composite Materials  

NASA Technical Reports Server (NTRS)

The applicability of existing test methods, which were developed primarily for laminates made of unidirectional prepreg tape, to textile composites is an area of concern. The issue is whether the values measured for the 2-D and 3-D braided, woven, stitched, and knit materials are accurate representations of the true material response. This report provides a review of efforts to establish a compression test method for textile reinforced composite materials. Experimental data have been gathered from several sources and evaluated to assess the effectiveness of a variety of test methods. The effectiveness of the individual test methods to measure the material's modulus and strength is determined. Data are presented for 2-D triaxial braided, 3-D woven, and stitched graphite/epoxy material. However, the determination of a recommended test method and specimen dimensions is based, primarily, on experimental results obtained by the Boeing Defense and Space Group for 2-D triaxially braided materials. They evaluated seven test methods: NASA Short Block, Modified IITRI, Boeing Open Hole Compression, Zabora Compression, Boeing Compression after Impact, NASA ST-4, and a Sandwich Column Test.

Masters, John E.

1996-01-01

110

Are natural fiber composites environmentally superior to glass fiber reinforced composites?  

Microsoft Academic Search

Natural fibers are emerging as low cost, lightweight and apparently environmentally superior alternatives to glass fibers in composites. We review select comparative life cycle assessment studies of natural fiber and glass fiber composites, and identify key drivers of their relative environmental performance. Natural fiber composites are likely to be environmentally superior to glass fiber composites in most cases for the

S. V Joshi; L. T Drzal; A. K Mohanty; S Arora

2004-01-01

111

Mimicry of natural material designs and processes  

NASA Astrophysics Data System (ADS)

Biological structural materials, although composed of unremarkable substances synthesized at low temperatures, often exhibit superior mechanical properties. In particular, the quality in which nearly all biologically derived materials excel is toughness. The advantageous mechanical properties are attributable to the hierarchical, composite, structural arrangements common to biological systems. Materials scientists and engineers have increasingly recognized that biological designs or processing approaches applied to man-made materials (biomimesis) may offer improvements in performance over conventional designs and fabrication methods. In this survey, the structures and processing routes of marine shells, avian eggshells, wood, bone, and insect cuticle are briefly reviewed, and biomimesis research inspired by these materials is discussed. In addition, this paper describes and summarizes the applications of biomineralization, self-assembly, and templating with proteins to the fabrication of thin ceramic films and nanostructure devices.

Bond, G. M.; Richman, R. H.; McNaughton, W. P.

1995-06-01

112

Theory of indentation on multiferroic composite materials  

NASA Astrophysics Data System (ADS)

This article presents a general theory on indentation over a multiferroic composite half-space. The material is transversely isotropic and magneto-electro-elastic with its axis of symmetry normal to the surface of the half-space. Based on the corresponding half-space Green's functions to point sources applied on the surface, explicit expressions for the generalized pressure vs. indentation depth are derived for the first time for the three common indenters (flat-ended, conical, and spherical punches). The important multiphase coupling issue is discussed in detail, with the weak and strong coupling being correctly revisited. The derived analytical solutions of indentation will not only serve as benchmarks for future numerical studies of multiphase composites, but also have important applications to experimental test and characterization of multiphase materials, in particular, of multiferroic properties.

Chen, Weiqiu; Pan, Ernian; Wang, Huiming; Zhang, Chuanzeng

2010-10-01

113

Endogenous plastic composite material in the Alzheimer's brain.  

PubMed

Accumulation of amyloid beta (Abeta) peptide in brain is the hallmark of Alzheimer's disease (AD). The resulting plaques though fibrous in nature may also consist of additional structures currently poorly defined. We hypothesize that plastic composite material contributes to plaque formation. This material is organized by polymers of acrolein, which is an oxidized lipid fragment found in AD. Acrolein, a 3-carbon compound, contains a carbonyl and a vinyl group that participate in polymerization via fundamental latex chemistry. The redox and surfactant properties of Abeta allow it to catalyze the polymerization of acrolein. We previously reported observations of thin plastic fragments of Abeta-polyacrolein. The current paper outlines the proposed steps in forming these plastic fragments. Endogenous plastic composite material may significantly contribute to the pathogenesis of AD. PMID:16678976

Seidler, N W; Craig, H D; Squire, T J

2006-01-01

114

Advanced Technology Composite Fuselage - Materials and Processes  

NASA Technical Reports Server (NTRS)

The goal of Boeing's Advanced Technology Composite Aircraft Structures (ATCAS) program was to develop the technology required for cost and weight efficient use of composite materials in transport fuselage structure. This contractor report describes results of material and process selection, development, and characterization activities. Carbon fiber reinforced epoxy was chosen for fuselage skins and stiffening elements and for passenger and cargo floor structures. The automated fiber placement (AFP) process was selected for fabrication of monolithic and sandwich skin panels. Circumferential frames and window frames were braided and resin transfer molded (RTM'd). Pultrusion was selected for fabrication of floor beams and constant section stiffening elements. Drape forming was chosen for stringers and other stiffening elements. Significant development efforts were expended on the AFP, braiding, and RTM processes. Sandwich core materials and core edge close-out design concepts were evaluated. Autoclave cure processes were developed for stiffened skin and sandwich structures. The stiffness, strength, notch sensitivity, and bearing/bypass properties of fiber-placed skin materials and braided/RTM'd circumferential frame materials were characterized. The strength and durability of cocured and cobonded joints were evaluated. Impact damage resistance of stiffened skin and sandwich structures typical of fuselage panels was investigated. Fluid penetration and migration mechanisms for sandwich panels were studied.

Scholz, D. B.; Dost, E. F.; Flynn, B. W.; Ilcewicz, L. B.; Nelson, K. M.; Sawicki, A. J.; Walker, T. H.; Lakes, R. S.

1997-01-01

115

Thermoplastic constructional composite material for radiation protection  

Microsoft Academic Search

The possibility of synthesis of filled metallooligomer powders on the basis of lead ethylsiliconate is considered by a method\\u000a of heterophase interaction, in siloksan chains of which chemically bound lead with a high concentration of atoms of lead is\\u000a contained. Thermoplastic constructional composite materials for radiation protection on the basis of a polystyrene polymeric\\u000a matrix modified by waterproof oligomer lead

V. I. Pavlenko; I. S. Epifanovskii; R. N. Yastrebinskii; O. V. Kuprieva

2011-01-01

116

The physical properties of composite materials  

Microsoft Academic Search

In this review, the physical properties of composite materials are discussed; however, discussion of the mechanical properties\\u000a has been excluded except when necessary for the consideration of properties such as thermal expansion or swelling and shrinkage.\\u000a One of the main aims in the review has been to show how the theoretical and experimental information that is already available\\u000a may be

D. K. Hale

1976-01-01

117

Alkali metal protective garment and composite material  

DOEpatents

A protective garment and composite material providing satisfactory heat resistance and physical protection for articles and personnel exposed to hot molten alkali metals, such as sodium. Physical protection is provided by a continuous layer of nickel foil. Heat resistance is provided by an underlying backing layer of thermal insulation. Overlying outer layers of fireproof woven ceramic fibers are used to protect the foil during storage and handling.

Ballif, III, John L. (Salt Lake City, UT); Yuan, Wei W. (Seattle, WA)

1980-01-01

118

Stresses around fasteners in composite materials  

NASA Astrophysics Data System (ADS)

Stress distributions around fasteners in composite materials were experimentally and theoretically studied. The fasteners were cheesehead and countersunk bolts. It was found that samples fastened with countersunk bolts tended to fatigue more rapidly than specimens with cheesehead bolts. Fewer fatigue cycles were needed for damage to initiate in plates with countersunk bolts, and higher direct stress and shear stress values are predicted to occur in plates with countersunk bolts. The principal failure mechanism was delamination, probably due to high direct and shear stresses.

Benchekchou, B.; White, R. G.

1993-04-01

119

ACEE Composite Structures Technology: Review of selected NASA research on composite materials and structures  

NASA Technical Reports Server (NTRS)

The NASA Aircraft Energy Efficiency (ACEE) Composite Primary Aircraft Structures Program was designed to develop technology for advanced composites in commercial aircraft. Research on composite materials, aircraft structures, and aircraft design is presented herein. The following parameters of composite materials were addressed: residual strength, damage tolerance, toughness, tensile strength, impact resistance, buckling, and noise transmission within composite materials structures.

1984-01-01

120

Fiber Reinforced Composite Materials Used for Tankage  

NASA Technical Reports Server (NTRS)

The Nonmetallic Materials and Processes Group is presently working on several projects to optimize cost while providing effect materials for the space program. One factor that must be considered is that these materials must meet certain weight requirements. Composites contribute greatly to this effort. Through the use of composites the cost of launching payloads into orbit will be reduced to one-tenth of the current cost. This research project involved composites used for aluminum pressure vessels. These tanks are used to store cryogenic liquids during flight. The tanks need some type of reinforcement. Steel was considered, but added too much weight. As a result, fiber was chosen. Presently, only carbon fibers with epoxy resin are wrapped around the vessels as a primary source of reinforcement. Carbon fibers are lightweight, yet high strength. The carbon fibers are wet wound onto the pressure vessels. This was done using the ENTEC Filament Winding Machine. It was thought that an additional layer of fiber would aid in reinforcement as well as containment and impact reduction. Kevlar was selected because it is light weight, but five times stronger that steel. This is the same fiber that is used to make bullet-proof vests trampolines, and tennis rackets.

Cunningham, Christy

2005-01-01

121

Impact of solids on composite materials  

NASA Technical Reports Server (NTRS)

The failure modes of composite materials as a result of low velocity impact were investigated by simulating the impact with a finite element analysis. An important facet of the project is the modeling of the impact of a solid onto cylindrical shells composed of composite materials. The model under development will simulate the delamination sustained when a composite material encounters impact from another rigid body. The computer equipment was installed, the computer network tested, and a finite element method model was developed to compare results with known experimental data. The model simulated the impact of a steel rod onto a rotating shaft. Pre-processing programs (GMESH and TANVEL) were developed to generate node and element data for the input into the three dimensional, dynamic finite element analysis code (DYNA3D). The finite element mesh was configured with a fine mesh near the impact zone and a coarser mesh for the impacting rod and the regions surrounding the impacting zone. For the computer simulation, five impacting loads were used to determine the time history of the stresses, the scribed surface areas, and the amount of ridging. The processing time of the computer codes amounted from 1 to 4 days. The calculated surface area were within 6-12 percent, relative error when compated to the actual scratch area.

Bronson, Arturo; Maldonado, Jerry; Chern, Tzong; Martinez, Francisco; Mccord-Medrano, Johnnie; Roschke, Paul N.

1987-01-01

122

Flexible Composite-Material Pressure Vessel  

NASA Technical Reports Server (NTRS)

A proposed lightweight pressure vessel would be made of a composite of high-tenacity continuous fibers and a flexible matrix material. The flexibility of this pressure vessel would render it (1) compactly stowable for transport and (2) more able to withstand impacts, relative to lightweight pressure vessels made of rigid composite materials. The vessel would be designed as a structural shell wherein the fibers would be predominantly bias-oriented, the orientations being optimized to make the fibers bear the tensile loads in the structure. Such efficient use of tension-bearing fibers would minimize or eliminate the need for stitching and fill (weft) fibers for strength. The vessel could be fabricated by techniques adapted from filament winding of prior composite-material vessels, perhaps in conjunction with the use of dry film adhesives. In addition to the high-bias main-body substructure described above, the vessel would include a low-bias end substructure to complete coverage and react peak loads. Axial elements would be overlaid to contain damage and to control fiber orientation around side openings. Fiber ring structures would be used as interfaces for connection to ancillary hardware.

Brown, Glen; Haggard, Roy; Harris, Paul A.

2003-01-01

123

Putting it Together: The Science and Technology of Composite Materials  

NSDL National Science Digital Library

Composite materials are light, strong, corrosion-resistant composites of two or more materials used commonly in manufacturing. This recent report is from the Australian Academy of Science with support from The Cooperative Research Centre for Advanced Composite Structures, Ltd. and the Commonwealth Department of Industry, Science and Resources. It gives information on the history, manufacturing techniques, and efficiency of composite materials. A glossary, reference list, and links to educational sites as well as other composite materials sites are also featured.

2000-01-01

124

Composite material systems for hydrogen management  

NASA Technical Reports Server (NTRS)

The task of managing hydrogen entry into elevated temperature structural materials employed in turbomachinery is a critical engineering area for propulsion systems employing hydrogen or decomposable hydrocarbons as fuel. Extant structural materials, such as the Inconel series, are embrittled by the ingress of hydrogen in service, leading to a loss of endurance and general deterioration of load-bearing dependability. Although the development of hydrogen-insensitive material systems is an obvious engineering option, to date insensitive systems cannot meet the time-temperature-loading service extremes encountered. A short-term approach that is both feasible and technologically sound is the development and employment of hydrogen barrier coatings. The present project is concerned with developing, analyzing, and physically testing laminate composite hydrogen barrier systems, employing Inconel 718 as the structural material to be protected. Barrier systems will include all metallic, metallic-to-ceramic, and, eventually, metallic/ceramic composites as the lamellae. Since space propulsion implies repetitive engine firings without earth-based inspection and repair, coating durability will be closely examined, and testing regimes will include repetitive thermal cycling to simulate damage accumulation. The target accomplishments include: generation of actual hydrogen permeation data for metallic, ceramic-metallic, and hybrid metallic/ceramic composition barrier systems, practically none of which is currently extant; definition of physical damage modes imported to barrier systems due to thermal cycling, both transient temperature profiles and steady-state thermal mismatch stress states being examined as sources of damage; and computational models that incorporate general laminate schemes as described above, including manufacturing realities such as porosity, and whatever defects are introduced through service and characterized during the experimental programs.

Pangborn, R. N.; Queeney, R. A.

1991-01-01

125

Energy absorbing hybrid nano-composite materials  

NASA Astrophysics Data System (ADS)

Base Epon 862 resin was enhanced with two types of fillers, graphitized carbon nanofiber (CNF) and silicon dioxide (SiO2) particles. The effect of both filler type and filler loading were investigated with respect to the energy absorbing capacity as well as the thermal stability of the hybrid composite material, measured in terms of the coefficient of thermal expansion (CTE). As well the composites with combinations of the fillers were evaluated for both enhanced damping and thermal stability, making it suitable for structural materials that need multiple functions. The composites were evaluated with dynamic mechanical analysis (DMA) to evaluate viscoelastic response, and using strain gauges to measure thermal strain responses. It has been found that the addition of 3wt% SiO2 along with 3wt% CNF can improve damping loss factors by up to 26% while at the same time improving thermal stability with reductions in CTE of up to 16.5%. Furthermore, these fillers loadings were successfully dispersed as received by mechanical mixing technique, making fabrication more economically suited to engineering applications.

Jang, Jae-Soon; Varischetti, Joshua; Lee, Gyo Woo; Suhr, Jonghwan

2009-03-01

126

Industry to Education Technical Transfer Program & Composite Materials. Composite Materials Course. Fabrication I Course. Fabrication II Course. Composite Materials Testing Course. Final Report.  

ERIC Educational Resources Information Center

These four reports provide details of projects to design and implement courses to be offered as requirements for the associate degree program in composites and reinforced plastics technology. The reports describe project activities that led to development of curricula for four courses: composite materials, composite materials fabrication I,…

Massuda, Rachel

127

Color masterbatch resin composition for packaging material for photographic photosensitive material and packaging material  

US Patent & Trademark Office Database

A color masterbach resin composition for a packaging material for a photographic photosensitive material which does not adversely affect photographic properties of the photographic photosensitive material, comprising a light-shielding material in a concentration thrice as much as or more that of the packaging material for a photographic photosensitive material, and a thermoplastic resin of which 50 wt. % or more is the same type as a thermoplastic resin occupying 50 wt. % or more of the total thermoplastic resin composing the packaging material for a photographic photosensitive material, production thereof, a packaging material for a photographic photosensitive material formed of a color masterbatch resin composition, and production thereof. In the color masterbatch resin composition and the packaging material for a photographic photosensitive material of the invention, light-shielding material is dispersed uniformly by employing a special resin composition, and thereby, adverse affects upon photographic hpotosensitive materials are prevented, and favorable appearance can be ensured. Moreover, fog with time, abnormal sensitivity, abrasion, pressure marks, etc. can be prevented.

1998-09-29

128

Composite Materials Instruction at the United States Naval Academy.  

National Technical Information Service (NTIS)

Composite materials are widely becoming the material of choice for many structural and nonstructural applications. The aircraft industry for example, has used composites for wing skins and other control surfaces that provide savings in fuel consumption an...

J. O. Barton, P. H. Miller

2003-01-01

129

Determination of moisture effects on impact properties of composite materials  

Microsoft Academic Search

Many applications of structural materials involving composites include impact or dynamic loading in a humid environment. Composite materials are known to degrade when subjected to humid conditions, and therefore the humidity confounds the difficulty of determining the high strain rate behavior of composites. Several researchers have found that water absorption by composites causes degradation of matrix dominated quasi-static properties. However,

E. Woldesenbet; N. Gupta; J. R. Vinson

2002-01-01

130

Use of advanced composite materials for innovative building design solutions/  

E-print Network

Advanced composite materials become popular in construction industry for the innovative building design solutions including strengthening and retrofitting of existing structures. The interface between different materials ...

Lau, Tak-bun, Denvid

2009-01-01

131

Filler Materials for Polyphenylenesulphide Composite Coatings: Preprint  

SciTech Connect

Researchers at Brookhaven National Laboratory and the National Renewable Energy Laboratory have tested polymer-based coating systems to reduce the capital equipment and maintenance costs of heat exchangers in corrosive and fouling geothermal environments. These coating systems act as barriers to corrosion to protect low-cost carbon steel tubing; they are formulated to resist wear from hydroblasting and to have high thermal conductivity. Recently, new filler materials have been developed for coating systems that use polyphenylenesulphide as a matrix. These materials include boehmite crystals (orthorhombic aluminum hydroxide, which is grown in situ as a product of reaction with the geothermal fluid), which enhance wear and corrosion resistance, and carbon fibers, which improve mechanical, thermal, and corrosion-resistance properties of the composite.

Sugama, T.; Gawlik, K.

2001-07-17

132

Composite materials flown on the Long Duration Exposure Facility  

NASA Technical Reports Server (NTRS)

Organic composite test specimens were flown on several LDEF experiments. Both bare and coated composites were flown. Atomic oxygen eroded bare composite material, with the resins being recessed at a greater rate than the fibers. Selected coating techniques protected the composite substrate in each case. Tensile and optical properties are reported for numerous specimens. Fiberglass and metal matrix composites were also flown.

George, Pete E.; Dursch, Harry W.; Pippin, H. Gary

1995-01-01

133

Degradation study of date palm fibre\\/polypropylene composites in natural and artificial weathering: mechanical and thermal analysis  

Microsoft Academic Search

Date palm leaves were compounded with polypropylene (PP) and UV stabilizers to form composite materials. The stability of the composites in natural weathering conditions of Saudi Arabia and in accelerated weathering conditions was investigated. The composites were found to be much more stable than PP under the severe natural weathering conditions of Saudi Arabia and in accelerated weathering trials. Compatibilized

B. F Abu-Sharkh; H Hamid

2004-01-01

134

ALL NATURAL COMPOSITE SANDWICH BEAMS FOR STRUCTURAL APPLICATIONS. (R829576)  

EPA Science Inventory

As part of developing an all natural composite roof for housing application, structural panels and unit beams were manufactured out of soybean oil based resin and natural fibers (flax, cellulose, pulp, recycled paper, chicken feathers) using vacuum assisted resin tran...

135

Composite material including nanocrystals and methods of making  

DOEpatents

Temperature-sensing compositions can include an inorganic material, such as a semiconductor nanocrystal. The nanocrystal can be a dependable and accurate indicator of temperature. The intensity of emission of the nanocrystal varies with temperature and can be highly sensitive to surface temperature. The nanocrystals can be processed with a binder to form a matrix, which can be varied by altering the chemical nature of the surface of the nanocrystal. A nanocrystal with a compatibilizing outer layer can be incorporated into a coating formulation and retain its temperature sensitive emissive properties

Bawendi, Moungi G. (Boston, MA); Sundar, Vikram C. (New York, NY)

2008-02-05

136

Viscoelastic behavior of fiber-reinforced composite materials undergoing cure  

E-print Network

A viscoelastic material model has been proposed to characterize the curing and thermal effects on the viscoelastic material properties of both the matrix material and the composite lamina. Micromechanics simulations are used to generate...

Wang, Kai

2012-06-07

137

Separating Mixtures: How We Concentrate Natural Materials  

NSDL National Science Digital Library

This activity involves separating mixtures of minerals on the basis of their physical properties. Students are shown a piece of granite and see that it is clearly a mixture. Students will try to devise ways of separating some simple mixtures and then see how some of the same methods are used to separate real minerals from mixtures. Students will discover that many useful materials are found as part of mixtures. For example, salt is found in underground deposits mixed with sand and clay. The mixture is called rock salt. Minerals are chemicals found naturally in the Earth and many of them are very useful. To get at the useful minerals, we usually have to separate them from less-useful material which are often called gangue (pronounced gang) by miners.

138

Lightweight Impact-Resistant Composite Materials: Lessons from Mantis Shrimp  

NASA Astrophysics Data System (ADS)

Nature has evolved efficient strategies to synthesize complex mineralized structures that exhibit exceptional damage tolerance. One such example is found in the hyper-mineralized hammer-like dactyl clubs of the stomatopods, a group of highly aggressive marine crustaceans. The dactyl clubs from one such species, Odontodactylus Scyllarus, exhibit an impressive set of characteristics adapted for surviving high velocity impacts with the heavily mineralized prey species on which they feed. Consisting of a multi-phase composite of oriented crystalline hydroxyapatite and amorphous calcium phosphate and carbonate, in conjunction with a highly expanded helicoidal organization of the fibrillar chitinous organic matrix, these structures display several effective lines of defense against catastrophic failure during repetitive high energy loading events. The study of this organism and its relatives has lead to design cues, which were incorporated into prototype composite materials designed for applications in aviation, body armor, and entertainment.

Milliron, Garrett Wayne

139

Composition and method for removing photoresist materials from electronic components  

DOEpatents

Composition and method for removing photoresist materials from electronic components. The composition is a mixture of at least one dense phase fluid and at least one dense phase fluid modifier. The method includes exposing a substrate to at least one pulse of the composition in a supercritical state to remove photoresist materials from the substrate.

Davenhall, Leisa B. (Santa Fe, NM); Rubin, James B. (Los Alamos, NM); Taylor, Craig M. V. (Jemez Springs, NM)

2008-06-03

140

Microrobotics Using Composite Materials: The Micromechanical Flying Insect Thorax  

E-print Network

Microrobotics Using Composite Materials: The Micromechanical Flying Insect Thorax R. J. Wood S, srinath, manas, ronf}@robotics.eecs.berkeley.edu Abstract The use of high performance composite materials, and higher stiffness to weight ratios than most metals. Composite structures yield remarkable improvements

Fearing, Ron

141

Composite materials: Tomorrow for the day after tomorrow  

NASA Technical Reports Server (NTRS)

A description is given of the history of the use of composite materials in the aerospace industry. Research programs underway to obtain exact data on the behavior of composite materials over time are discussed. It is concluded that metal composites have not yet replaced metals, but that that this may be a future possibility.

Condom, P.

1982-01-01

142

NDE Elastic Properties of Fiber-Reinforced Composite Materials  

NASA Technical Reports Server (NTRS)

Fiber-reinforced composites are increasingly replacing metallic alloys as structural materials for primary components of fracture-critical structures. This trend is a result of the growing understanding of material behavior and recognition of the desirable properties of composites. A research program was conducted on NDE methods for determining the elastic properties of composites.

Bar-Cohen, Y.

1995-01-01

143

Use of finite element in micromechanics of natural composites  

Microsoft Academic Search

The finite element method is demonstrated as an analytical method for micromechanics of natural composites. This study illustrates the use of the finite element method to investigate stiffness, transverse modulus, stress concentration, delamination and crack propagation of a single-ply natural composite from constituent properties.

J. E. Saliba

1996-01-01

144

Properties of natural fiber composites made by pultrusion process  

Microsoft Academic Search

Great efforts are being made at Brunel University, UK in attempt to develop natural fiber composites with desired structure and good overall properties for construction. This work focuses on the mechanical and morphological characterization of the pultruded composite rods made from hemp and wool fiber reinforcements. The results showed that the composite using polyurethane resin system has higher specific tensile

Xi Peng; Mizi Fan; John Hartley; Majeed Al-Zubaidy

2012-01-01

145

High Performance Abrasion-Resistant Materials: Lessons from Nature  

E-print Network

composites is to learn from nature about how to control the synthesis of the nano- and micro-composite made of polycrystalline magnetite nanorods surrounded by ?-chitin layers. By identifying the local micro-

Wang, Qianqian

2012-01-01

146

Multi-scale Modeling for Piezoelectric Composite Materials  

E-print Network

In this paper, we focus on multi-scale modeling and simulation of piezoelectric composite materials. A multi-scale model for piezoelectric composite materials under the framework of Heterogeneous Multi-scale Method(HMM) is proposed. For materials with periodic microstructure, macroscopic model is derived from microscopic model of piezoelectric composite material by asymptotic expansion. Convergence analysis under the framework of homogenization theory is carried out. Moreover, error estimate between HMM solutions and homogenization solutions is derived. A 3-D numerical example of 1-3 type piezoelectric composite materials is employed to verify the error estimate.

Qian Zhang; Xingye Yue

2014-02-02

147

New High Performance Natural Fiber Composites  

Microsoft Academic Search

Cellulose fiber composites have been used ex- tensively for the construction industries in North Ameri- ca and they began to receive very much attraction in Eu- rope, South America and Asia. In order to increase the competitiveness, it is important for the composites indus- try to reduce the consumption of energy and cost as well as to improve output and

J. Denault; F. Perrin; W. Hu

148

Tailoring The Microwave Permittivity And Permeability Of Composite Materials  

E-print Network

selective surfaces such as bandpass and lowpass filters as well as radar absorbing materials1 Tailoring The Microwave Permittivity And Permeability Of Composite Materials Kenneth M. Bober/Lowell, Lowell, MA 01854 ABSTRACT The microwave permittivity( r ) and permeability( r ) of composite materials

Massachusetts at Lowell, University of

149

Using of Composite Material in Wind Turbine Blades  

Microsoft Academic Search

The turbines manufactured from the mid 1980s until the late 1990s were mainly constructed using standard components. After that period, special components started being designed and manufactured for turbine use only. One of the best solutions is using composite materials in wind turbine. Most composites are made up of just two materials. One material (the matrix or binder) binds together

Bulent Eker; Aysegul Akdogan; Ali Vardar

2006-01-01

150

High strain-rate behavior of natural fiber-reinforced polymer composites  

Microsoft Academic Search

The high strain-rate constitutive behavior of polymer composites with various natural fibers is studied. Hemp, hemp\\/glass hybrid, cellulose, and wheat straw-reinforced polymeric composites have been manufactured, and a split-Hopkinson pressure bar apparatus has been designed to measure the dynamic stress–strain response of the materials. Using the apparatus, compressive stress–strain curves have been obtained that reveal the materials’ constitutive characteristics at

Wonsuk Kim; Alan Argento; Ellen Lee; Cynthia Flanigan; Daniel Houston; Angela Harris; Deborah F Mielewski

2012-01-01

151

A Review on the Natural Fiber-Reinforced Polymer Composites for the Development of Roselle Fiber-Reinforced Polyester Composite  

Microsoft Academic Search

In recent years, the interest of scientists and engineers has turned over on utilizing all plant fibers as effectively and economically as possible to produce good quality fiber-reinforced polymer composites for structural, building, and other needs. It is because of the high availability of the natural resources in this green world. This has led to the development of alternative materials

M. Thiruchitrambalam; A. Athijayamani; S. Sathiyamurthy; A. Syed Abu Thaheer

2010-01-01

152

Nature of branching in disordered materials  

NASA Astrophysics Data System (ADS)

The phenomenon of structural branching is ubiquitous in a wide array of materials such as polymers, ceramic aggregates, networks and gels. These materials with structural branching are a unique class of disordered materials and often display complex architectures. Branching has a strong influence over the structure-property relationships of these materials. Despite the generic importance across a wide spectrum of materials, our physical understanding of the scientific nature of branching and the analytic description and quantification of branching is at an early stage, though many decades of effort have been made. For polymers, branching is conventionally characterized by hydrodynamic radius (size exclusion chromatography, SEC, rheology) or by counting branch sites (nuclear magnetic resonance spectroscopy, NMR). SEC and rheology are, at best, qualitative; and quantitative characterization techniques like NMR and transmission electron microscopy (TEM) (for ceramic nanoparticulate aggregates) have limitations in providing routine quantification. Effective structure characterization, though an important step in understanding these materials, remains elusive. For ceramic aggregates, theoretical work has dominated and only a few publications on analytic studies exist to support theory. A new generic scaling model is proposed in Chapter I, which encompasses the critical structural features associated with these complex architectures. The central theme of this work is the application of this model to describe a variety of disordered structures like aggregated nano-particulates, long chain branched polymers like polyethylene, hyperbranched polymers, multi-arm star polymers, and cyclic macromolecules. The application of the proposed model to these materials results in a number of fundamental structural parameters, like the mass-fractal dimension, df, the minimum path dimension, dmin, connectivity dimension, c, and the mole fraction branch content, ?br. These dimensions reflect different features of the global structure, and it is categorically shown that this dimensional analysis results in effective structure characterization of these materials. Small-angle scattering of x-rays and neutrons can be used to quantify branch content and characterize the structure, through application of concepts native to fractal geometry. The application of the scaling model to nano-particulate aggregates yields quantitative information regarding the structure of these materials. In-situ small and ultra small angle x-ray scattering data collected on fumed silica and soot particles is presented in Chapter II. These measurements were performed at Advanced Photon Source, Argonne National Laboratory, UNICAT beam-line and the European Synchrotron Radiation Facility, Grenoble, France, ID2 beam-line. The dimensional analysis is successful in not only giving an average snap-shot of the nano-particulate aggregates, but also yields information regarding the growth processes involved in the complex pyrolysis technique of synthesizing these materials. In case of macromolecular systems, the minimum path dimension, dmin, is shown to reflect the thermodynamics of the system. This is categorically established in Chapter III on hyperbranched polymers, where the scaling model accurately predicts the good-solvent to theta-condition transition in these highly branched polymers with increasing molar mass. The scaling model is applied to the long standing problem of quantifying long chain branching in polyethylene in Chapter IV. Small angle neutron scattering data on dilute solutions of polyethylene were obtained at the Intense Pulsed Neutron Source (SAND beam-line); NIST center for Neutron Scattering (NG3 beam-line); and Los Alamos Neutron Scattering Center (LQD beam-line). This work, for the first time in literature, reports the length of a long chain branch in polyethylene in terms of the average molar mass of the branches, and the average number of carbon atoms in the long chain branch. Cyclic polymers are examined in the Chapter V. The scaling model presents a new

Kulkarni, Amit S.

153

Designing nacre-like materials for simultaneous stiffness, strength and toughness: Optimum materials, composition, microstructure and size  

NASA Astrophysics Data System (ADS)

Nacre, bone and spider silk are staggered composites where inclusions of high aspect ratio reinforce a softer matrix. Such staggered composites have emerged through natural selection as the best configuration to produce stiffness, strength and toughness simultaneously. As a result, these remarkable materials are increasingly serving as model for synthetic composites with unusual and attractive performance. While several models have been developed to predict basic properties for biological and bio-inspired staggered composites, the designer is still left to struggle with finding optimum parameters. Unresolved issues include choosing optimum properties for inclusions and matrix, and resolving the contradictory effects of certain design variables. Here we overcome these difficulties with a multi-objective optimization for simultaneous high stiffness, strength and energy absorption in staggered composites. Our optimization scheme includes material properties for inclusions and matrix as design variables. This process reveals new guidelines, for example the staggered microstructure is only advantageous if the tablets are at least five times stronger than the interfaces, and only if high volume concentrations of tablets are used. We finally compile the results into a step-by-step optimization procedure which can be applied for the design of any type of high-performance staggered composite and at any length scale. The procedure produces optimum designs which are consistent with the materials and microstructure of natural nacre, confirming that this natural material is indeed optimized for mechanical performance.

Barthelat, Francois

2014-12-01

154

Acoustical and fire-retardant properties of jute composite materials  

Microsoft Academic Search

This research aims to study the acoustical and flammability properties of biodegradable and easily disposable natural fibre jute and its composite for noise reduction in house hold appliances, automotive and architectural applications. Acoustical properties of jute fibre and felt (natural rubber latex jute composite) were measured in terms of normal specific sound absorption coefficient and sound transmission loss whereas fire

S. Fatima; A. R. Mohanty

2011-01-01

155

CCMR: â Green â Composites: An alternative to petroleum-based materials  

NSDL National Science Digital Library

Composites made from natural fibers and resins offer a potential alternative to the petroleum-based materials that are currently used in in many applications such as packaging. These composites have the advantage of being biodegradable, renewable and environmentally friendly. In this work, different additives, including glycerol and polycarboxylic acid (PCA), are introduced to these composites in an attempt to increase properties such as strength and flexibility.

Cooley, Ladean M.

2007-08-29

156

Natural Shock Sintering of Unconsolidated Planetary Materials  

NASA Astrophysics Data System (ADS)

On Earth, the transformation of unconsolidated sediment (e.g., sand) to rock (sandstone) occurs via the process of lithification. Lithification typically occurs via burial within the upper crust at less than 150 degrees celsius, at depths of less than 5 km in the presence of liquid H2O. Liquid H2O is often important in the process of lithification because it is the transporting medium for dissolved and suspended ions and mineral species, which eventually precipitate as a cement that binds the unconsolidated grains. Lithification also applies to sedimentary deposits formed by precipitation of minerals from aqueous solutions at surface, or near- surface, conditions (e.g., to generate sulfate or carbonate-rich evaporites). However, for many planetary bodies in our solar system, there are no large sources of liquid H2O to facilitate this type of lithification process. Despite the absence of water on such bodies, the development of consolidated fragmental material is commonplace and it probably dominates the surface materials of Mercury, the Moon, Mars and many asteroids. This material, typically in the form of breccias, is a relatively coherent rock, yet the nature of the "glue" that binds the fragments is not well understood. Clearly, other processes are responsible for the lithification that we take for granted in many of the sedimentary rocks developed on our wet planet. This work explores these processes. For certain planetary bodies unconsolidated material may be bound by ices, such that it possesses rock-like properties in terms in strength and behaviour. In the absence of H2O, unconsolidated semi-molten material can be lithified by welding and compaction (e.g., certain pyroclastic discharges that fall and accumulate to form ignimbrites). This requires the production of hot volcanogenic or impact ejecta. In this work we explore the nature of the binding medium in different types of lunar breccia collected during the Apollo15, 16 and 17 missions, in meteorites of the howardite, eucrite and diogenite (HED) class and in laboratory shocked lunar regolith samples. Analytical scanning electron microscopy (SEM) and field emission SEM are used to explore the microstructures. The samples are grouped as: (1) being primarily derived from unconsolidated lunar regolith; (2) impact melt rocks, and (3) samples that were primarily derived from solid rock that were impact brecciated. There is significant overlap between these groups. All may exhibit relatively high degrees of porosity, especially regoliths and breccias. Features that affect the cohesiveness and coherence of the rock product are given particular attention. For this study, bridges are necks between grains, intergranular melts are melts that have developed between grains, fused grains are grains that are joined at a contact interfaces with no visible neck, and annealed fractures are fractures that have been partially or totally closed by either diffusion across the fracture or melting either side of the fracture. The various mechanisms of lithification are explored and discussed. Localized heating appears to be the dominant welding process. Heat generation can be attributed to (a) energy release due to frictional movement between grains during bulk (impact-generated) compression and (b) shock wave energy dissipation, especially between grains with high impedance contrasts and at grain (and other microstructural) boundaries. For unconsolidated materials, the resultant microtextures are akin to products of the industrial shock sintering of powders, and analogies are drawn between these two processes.

Spray, J. G.

2006-12-01

157

Material, process, and product design of thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

Thermoplastic composites made of polypropylene (PP) and E-glass fibers were investigated experimentally as well as theoretically for two new classes of product designs. The first application was for reinforcement of wood. Commingled PP/glass yarn was consolidated and bonded on wood panel using a tie layer. The processing parameters, including temperature, pressure, heating time, cooling time, bonding strength, and bending strength were tested experimentally and evaluated analytically. The thermoplastic adhesive interface was investigated with environmental scanning electron microscopy. The wood/composite structural design was optimized and evaluated using a Graphic Method. In the second application, we evaluated use of thermoplastic composites for explosion containment in an arrester. PP/glass yarn was fabricated in a sleeve form and wrapped around the arrester. After consolidation, the flexible composite sleeve forms a solid composite shell. The composite shell acts as a protection layer in a surge test to contain the fragments of the arrester. The manufacturing process for forming the composite shell was designed. Woven, knitted, and braided textile composite shells made of commingled PP/glass yarn were tested and evaluated. Mechanical performance of the woven, knitted, and braided composite shells was examined analytically. The theoretical predictions were used to verify the experimental results.

Dai, Heming

158

Natural Cork Agglomerate Employed as an Environmentally Friendly Solution for Quiet Sandwich Composites  

PubMed Central

Carbon fiber-synthetic foam core sandwich composites are widely used for many structural applications due to their superior mechanical performance and low weight. Unfortunately these structures typically have very poor acoustic performance. There is increasingly growing demand in mitigating this noise issue in sandwich composite structures. This study shows that marrying carbon fiber composites with natural cork in a sandwich structure provides a synergistic effect yielding a noise-free sandwich composite structure without the sacrifice of mechanical performance or weight. Moreover the cork-core sandwich composites boast a 250% improvement in damping performance, providing increased durability and lifetime operation. Additionally as the world seeks environmentally friendly materials, the harvesting of cork is a natural, renewable process which reduces subsequent carbon footprints. Such a transition from synthetic foam cores to natural cork cores could provide unprecedented improvements in acoustic and vibrational performance in applications such as aircraft cabins or wind turbine blades. PMID:22574250

Sargianis, James; Kim, Hyung-ick; Suhr, Jonghwan

2012-01-01

159

Some functional properties of composite material based on scrap tires  

NASA Astrophysics Data System (ADS)

The utilization of scrap tires still obtains a remarkable importance from the aspect of unloading the environment from non-degradable waste [1]. One of the most prospective ways for scrap tires reuse is a production of composite materials [2] This research must be considered as a continuation of previous investigations [3, 4]. It is devoted to the clarification of some functional properties, which are considered important for the view of practical applications, of the composite material. Some functional properties of the material were investigated, for instance, the compressive stress at different extent of deformation of sample (till 67% of initial thickness) (LVS EN 826) [5] and the resistance to UV radiation (modified method based on LVS EN 14836) [6]. Experiments were realized on the purposefully selected samples. The results were evaluated in the correlation with potential changes of Shore C hardness (Shore scale, ISO 7619-1, ISO 868) [7, 8]. The results showed noticeable resistance of the composite material against the mechanical influence and ultraviolet (UV) radiation. The correlation with the composition of the material, activity of binder, definite technological parameters, and the conditions supported during the production, were determined. It was estimated that selected properties and characteristics of the material are strongly dependent from the composition and technological parameters used in production of the composite material, and from the size of rubber crumb. Obtained results show possibility to attain desirable changes in the composite material properties by changing both the composition and technological parameters of examined material.

Plesuma, Renate; Malers, Laimonis

2013-09-01

160

Composite materials: Fatigue and fracture. Vol. 3  

NASA Technical Reports Server (NTRS)

The present volume discusses topics in the fields of matrix cracking and delamination, interlaminar fracture toughness, delamination analysis, strength and impact characteristics, and fatigue and fracture behavior. Attention is given to cooling rate effects in carbon-reinforced PEEK, the effect of porosity on flange-web corner strength, mode II delamination in toughened composites, the combined effect of matrix cracking and free edge delamination, and a 3D stress analysis of plain weave composites. Also discussed are the compression behavior of composites, damage-based notched-strength modeling, fatigue failure processes in aligned carbon-epoxy laminates, and the thermomechanical fatigue of a quasi-isotropic metal-matrix composite.

O'Brien, T. K. (editor)

1991-01-01

161

Alternative methods for determination of composition and porosity in abradable materials  

Microsoft Academic Search

Materials properties and performance are governed by their composition and structure. These are commonly characterized using materialography and image analysis. However, in abradable materials, obtaining a reliable and representative sample (polished section) for this widespread technique is complicated by their abradable nature and heterogeneity. Therefore, alternative methods are also considered in this paper. They are namely X-ray diffraction and electron

Ji?í Mat?jí?ek; Blahoslav Kolman; Ji?í Dubský; Karel Neufuss; Noel Hopkins; Jochen Zwick

2006-01-01

162

Electromagnetic properties of Permendur granular composite materials containing flaky particles  

NASA Astrophysics Data System (ADS)

Electromagnetic properties of Permendur (Fe50Co50 alloy) granular composite materials containing flaky particle have been studied from the RF to microwave frequency range. Properties of the flaky particle composites were compared with the spherical particle ones. The electrical conductivity of the flaky particle composite was higher than that of the spherical particle composite at the same particle content. An insulator to metal transition was observed at the percolation threshold ?c in both composites. The ?c of the flaky particle composite was lower than that of the spherical one. The relative complex permittivity indicates that the insulating state has dielectric properties. For the spherical particle composite, the permittivity enhancement caused by particle cluster formation can be described by the effective cluster model (ECM). The enhancement of the dielectric constant in the flaky particle composite is larger than the ECM prediction. A negative permittivity spectrum indicating a low frequency plasmonic state was observed in the metallic 70 vol. % flaky particle composite. The relative complex permeability spectra of the flaky particle composite are different from those of the spherical one. The flaky particle composite shows a larger permeability value and lower permeability dispersion frequency than the spherical particle composite. Negative permeability spectra were observed in the both composite materials. The negative permeability frequency band of the flaky particle composite is lower than that of the spherical particle composite owing to the demagnetizing field effect.

Kasagi, Teruhiro; Tsutaoka, Takanori; Hatakeyama, Kenichi

2014-10-01

163

Controlling Performance of Laminated Composites Using Piezoelectric Materials  

E-print Network

-electro-elastic constitutive model for transversely isotropic materials is used for each ply in the composite laminates. The first-ply failure and ultimate laminate failure criteria of composite laminates are used to predict the failure stress and mode of the composite...

Hasan, Zeaid

2012-02-14

164

Structural assessment of a novel carpet composite material  

NASA Astrophysics Data System (ADS)

Noise pollution caused by vehicles has always been a concern to the communities in the vicinity of highways and busy roadways. The carpet composite material was recently developed and proposed to be utilized as sound-walls in highways. In the carpet composite material post-consumer carpet is used as reinforcing element inside and epoxy matrix. The main focus of this work is to assess flexural behavior of this novel material. Tests were performed on the individual components of the composite material. Using the results from the test and a theoretical approach, a model was proposed that describes the flexural behavior and also a close estimate of the flexural strength of the carpet composite material. In this work the contribution of the carpet in flexural behavior of the composite material was investigated. It was found that the carpet is weaker than the epoxy and the contribution of the carpet in flexural strength of the composite material is small. It was also found that using the carpet inside the epoxy results in 63% decrease in ultimate strength of the section, however; the gain in ductility is considerable. Based on the flexural test results the composite section follows a bilinear behavior. To determine the capacity of the composite, the effective epoxy section is to be determined before and after the tension cracks form at the bottom of the section. Using the epoxy section analysis described in this work, the strength of the composite section can be calculated at cracking and ultimate capacity.

Abbaszadeh, Ali

165

Discrimination of naturally occurring radioactive material in plastic scintillator material  

Microsoft Academic Search

Plastic scintillator material is used in many applications for the detection of gamma rays from radioactive material, primarily due to the sensitivity per unit cost compared to other detection materials. However, the resolution and lack of full-energy peaks in the plastic scintillator material prohibits detailed spectroscopy. Therefore, other materials such as doped sodium iodide are used for spectroscopic applications. The

J. H. Ely; R. T. Kouzes; B. D. Geelhood; J. E. Schweppe; R. A. Warner

2004-01-01

166

American Nature Writing and the Composition Classroom.  

ERIC Educational Resources Information Center

A model for an integrative first-year writing class, combining American native writing, field experience, and the fundamental trappings of a composition class, are examined in this paper. Students can learn to respond to environmental issues in creative ways and explore issues that they will face in their lives. In addition to a combined…

Ryan, Jack

167

Composite materials for precision space reflector panels  

Microsoft Academic Search

One of the critical technology needs of large precision reflectors for future astrophysical and optical communications satellites lies in the area of structural materials. Results from a materials research and development program at NASA Langley Research Center to provide materials for these reflector applications are discussed. Advanced materials that meet the reflector panel requirements are identified and thermal, mechanical and

Stephen S. Tompkins; Joan G. Funk; David E. Bowles; Timothy W. Towell; John W. Connell

1992-01-01

168

Evaluation of Composite Materials for Use on Launch Complexes  

NASA Technical Reports Server (NTRS)

Commercially available composite structural shapes were evaluated for use. These composites, fiberglass-reinforced polyester and vinylester resin materials are being used extensively in the fabrication and construction of low maintenance, corrosion resistant structures. The evaluation found that in many applications these composite materials can be successfully used at the space center. These composite materials should not be used where they will be exposed to the hot exhaust plume/cloud of the launch vehicle during the liftoff, and caution should be taken in their use in areas where electrostatic discharge and hypergolic propellant compatibility are primary concerns.

Finchum, A.; Welch, Peter J.

1989-01-01

169

Process for fabricating composite material having high thermal conductivity  

DOEpatents

A process for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost.

Colella, Nicholas J. (Livermore, CA); Davidson, Howard L. (San Carlos, CA); Kerns, John A. (Livermore, CA); Makowiecki, Daniel M. (Livermore, CA)

2001-01-01

170

Advanced organic composite materials for aircraft structures: Future program  

NASA Technical Reports Server (NTRS)

Revolutionary advances in structural materials have been responsible for revolutionary changes in all fields of engineering. These advances have had and are still having a significant impact on aircraft design and performance. Composites are engineered materials. Their properties are tailored through the use of a mix or blend of different constituents to maximize selected properties of strength and/or stiffness at reduced weights. More than 20 years have passed since the potentials of filamentary composite materials were identified. During the 1970s much lower cost carbon filaments became a reality and gradually designers turned from boron to carbon composites. Despite progress in this field, filamentary composites still have significant unfulfilled potential for increasing aircraft productivity; the rendering of advanced organic composite materials into production aircraft structures was disappointingly slow. Why this is and research and technology development actions that will assist in accelerating the application of advanced organic composites to production aircraft is discussed.

1987-01-01

171

Industry technology assessment of graphite-polymide composite materials. [conferences  

NASA Technical Reports Server (NTRS)

An assessment of the current state of the art and the future prospects for graphite polyimide composite material technology is presented. Presentations and discussions given at a minisymposium of major issues on the present and future use, availability, processing, manufacturing, and testing of graphite polyimide composite materials are summarized.

1975-01-01

172

NEW ECO-FRIENDLY HYBRID COMPOSITE MATERIALS FOR CIVIL CONSTRUCTION  

Microsoft Academic Search

This paper concerns the development of new hybrid composite materials using granulated cork, a by-product of cork industry, cellulose pulp, from recycling of paper residues, and hemp fibres. The binder used is either cellulose pulp or lime-pozzolan mixture. Such materials may be used as composite boards and mortars for non structural elements of construction, such as dry walls and ceiling

R. Eires; J. P. Nunes; R. Fangueiro; S. Jalali; A. Camões

173

Pistons and Cylinders Made of Carbon-Carbon Composite Materials  

NASA Technical Reports Server (NTRS)

An improved reciprocating internal combustion engine has a plurality of engine pistons, which are fabricated from carbon---carbon composite materials, in operative association with an engine cylinder block, or an engine cylinder tube, or an engine cylinder jug, all of which are also fabricated from carbon-carbon composite materials.

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor); Schwind, Francis A. (Inventor)

2000-01-01

174

Pistons and Cylinders Made of Carbon-Carbon Composite Materials  

NASA Technical Reports Server (NTRS)

An improved reciprocating internal combustion engine has a plurality of engine pistons, which are fabricated from carbon-carbon composite materials, in operative association with an engine cylinder block, or an engine cylinder tube, or an engine cylinder jug, all of which are also fabricated from carbon-carbon composite materials.

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor); Schwind, Francis A. (Inventor)

2000-01-01

175

Progressive failure analysis of fibrous composite materials and structures  

NASA Technical Reports Server (NTRS)

A brief description is given of the modifications implemented in the PAFAC finite element program for the simulation of progressive failure in fibrous composite materials and structures. Details of the memory allocation, input data, and the new subroutines are given. Also, built-in failure criteria for homogeneous and fibrous composite materials are described.

Bahei-El-din, Yehia A.

1990-01-01

176

Characterization and prediction of abrasive wear of powder composite materials  

Microsoft Academic Search

Composite materials produced by powder metallurgy provide a solution in many engineering applications where materials with high abrasion and erosion resistance are required. The actual wear behaviour of the material is associated with many external factors (particle size, velocity, angularity, etc.) and intrinsic material properties (hardness, toughness, Young modulus, etc.). Hardness and toughness properties of such tribomaterials are highly dependent

R. Veinthal; P. Kulu; J. Pirso; H. Käerdi

2009-01-01

177

Application of advanced material systems to composite frame elements  

NASA Technical Reports Server (NTRS)

A three phase program has been conducted to investigate DuPont's Long Discontinuous Fiber (LDF) composites. Additional tests were conducted to compare LDF composites against toughened thermosets and a baseline thermoset system. Results have shown that the LDF AS4/PEKK offers improved interlaminar (flange bending) strength with little reduction in mechanical properties due to the discontinuous nature of the fibers. In the third phase, a series of AS4/PEKK LDF C-section curved frames (representing a typical rotorcraft light frame) were designed, manufactured and tested. Specimen reconsolidation after 'stretch forming' and frame thickness were found to be key factors in this light frame's performance. A finite element model was constructed to correlate frame test results with expected strain levels determined from material property tests. Adequately reconsolidated frames performed well and failed at strain levels at or above baseline thermoset material test strains. Finally a cost study was conducted which has shown that the use of LDF for this frame would result in a significant cost savings, for moderate to large lot sizes compared with the hand lay-up of a thermoset frame.

Llorente, Steven; Minguet, Pierre; Fay, Russell; Medwin, Steven

1992-01-01

178

Natural fiber composites with plant oil-based resin  

Microsoft Academic Search

Vacuum-assisted resin transfer molding or resin vacuum infusion process was used to make composite panels out of plant oil-based resin [acrylated epoxidized soybean oil (AESO)] and natural fiber mats made of flax, cellulose, pulp and hemp. The composites formed by room temperature cure with natural fiber reinforcement of about 10–50 wt% increased the flexural modulus to a range between 1.5

A O'Donnell; M. A Dweib; R. P Wool

2004-01-01

179

ROLE OF FIBER MODIFICATION IN NATURAL FIBER COMPOSITE PROCESSING  

Microsoft Academic Search

The prediction and characterization of the adhesion between fiber, surface treatment, and polymer is critical to the success of large-scale natural fiber based polymer composites in automotive semi-structural application. The two primary factors limiting the use of natural fiber in polymer composites are fiber moisture uptake and fiber degradation during high-temperature processing. In this study, we have developed several fiber

Leonard S. Fifield; Kayte M. Denslow; Anna Gutowska; Kevin L. Simmons; Jim Holbery

2005-01-01

180

Preparation and properties of recycled HDPE\\/natural fiber composites  

Microsoft Academic Search

Composites based on recycled high density polyethylene (RHDPE) and natural fibers were made through melt blending and compression molding. The effects of the fibers (wood and bagasse) and coupling agent type\\/concentration on the composite properties were studied. The use of maleated polyethylene (MAPE), carboxylated polyethylene (CAPE), and titanium-derived mixture (TDM) improved the compatibility between the bagasse fiber and RHDPE, and

Yong Lei; Qinglin Wu; Fei Yao; Yanjun Xu

2007-01-01

181

Advanced composite structures. [metal matrix composites - structural design criteria for spacecraft construction materials  

NASA Technical Reports Server (NTRS)

A monograph is presented which establishes structural design criteria and recommends practices to ensure the design of sound composite structures, including composite-reinforced metal structures. (It does not discuss design criteria for fiber-glass composites and such advanced composite materials as beryllium wire or sapphire whiskers in a matrix material.) Although the criteria were developed for aircraft applications, they are general enough to be applicable to space vehicles and missiles as well. The monograph covers four broad areas: (1) materials, (2) design, (3) fracture control, and (4) design verification. The materials portion deals with such subjects as material system design, material design levels, and material characterization. The design portion includes panel, shell, and joint design, applied loads, internal loads, design factors, reliability, and maintainability. Fracture control includes such items as stress concentrations, service-life philosophy, and the management plan for control of fracture-related aspects of structural design using composite materials. Design verification discusses ways to prove flightworthiness.

1974-01-01

182

Buckling analyses of composite laminate skew plates with material nonlinearity  

Microsoft Academic Search

A nonlinear material constitutive model, including a nonlinear in-plane shear formulation and the Tsai–Wu failure criterion, for fiber–composite laminate materials is employed to carry out finite element buckling analyses for composite laminate skew plates under uniaxial compressive loads. The influences of laminate layup, plate skew angle and plate aspect ratio on the buckling resistance of composite laminate skew plates are

Hsuan-Teh Hu; Chia-Hao Yang; Fu-Ming Lin

2006-01-01

183

21 CFR 878.3500 - Polytetrafluoroethylene with carbon fibers composite implant material.  

Code of Federal Regulations, 2010 CFR

... Polytetrafluoroethylene with carbon fibers composite implant material... Polytetrafluoroethylene with carbon fibers composite implant material...A polytetrafluoroethylene with carbon fibers composite implant...

2010-04-01

184

Nano composite phase change materials microcapsules  

NASA Astrophysics Data System (ADS)

MicroPCMs with nano composite structures (NC-MicroPCMs) have been systematically studied. NC-MicroPCMs were fabricated by the in situ polymerization and addition of silver NPs into core-shell structures. A full factorial experiment was designed, including three factors of core/shell, molar ratio of formaldehyde/melamine and NPs addition. 12 MicroPCMs samples were prepared. The encapsulated efficiency is approximately 80% to 90%. The structural/morphological features of the NC-MicroPCMs were evaluated. The size was in a range of 3.4 mu m to 4.0 mu m. The coarse appearance is attributed to NPs and NPs are distributed on the surface, within the shell and core. The NC-MicroPCMs contain new chemical components and molecular groups, due to the formation of chemical bonds after the pretreatment of NPs. Extra X-ray diffraction peaks of silver were found indicating silver nano-particles were formed into an integral structure with the core/shell structure by means of chemical bonds and physical linkages. Extra functionalities were found, including: (1) enhancement of IR radiation properties; (2) depression of super-cooling, and (3) increase of thermal stabilities. The effects of SERS (Surface Enhanced Raman Spectroscopy) arising from the silver nano-particles were observed. The Raman scattering intensity was magnified more than 100 times. These effects were also exhibited in macroscopic level in the fabric coatings as enhanced IR radiation properties were detected by the "Fabric Infrared Radiation Management Tester" (FRMT). "Degree of Crystallinity" (DOC) was measured and found the three factors have a strong influence on it. DOC is closely related to thermal stability and MicroPCMs with a higher DOC show better temperature resistance. The thermal regulating effects of the MicroPCMs coatings were studied. A "plateau regions" was detected around the temperature of phase change, showing the function of PCMs. Addition of silver nano-particles to the MicroPCMs has a positive influence on it. NC-MicroPCMs with introducing silver nano particles into the MicroPCMs structure, have shown excellent multifunctional thermal properties and thermal stabilities that are far beyond those of the conventional MicroPCMs. The novel NC-MicroPCMs can be used to develop advanced smart materials and products with prosperous and promising applications in a number of industries.

Song, Qingwen

185

Corrosion inhibiting composition for treating asbestos containing materials  

DOEpatents

A composition for transforming a chrysotile asbestos-containing material into a non-asbestos material is disclosed. The composition comprises water, at least about 30% by weight of an acid component, optionally a source of fluoride ions, and a corrosion inhibiting amount of thiourea, a lower alkylthiourea, a C{sub 8}{single_bond}C{sub 15} alkylpyridinium halide or mixtures. A method of transforming an asbestos-containing building material, while part of a building structure, into a non-asbestos material by using the present composition also is disclosed.

Hartman, J.R.

1998-04-21

186

Nondestructive evaluation of composite materials - A design philosophy  

NASA Technical Reports Server (NTRS)

Efficient and reliable structural design utilizing fiber reinforced composite materials may only be accomplished if the materials used may be nondestructively evaluated. There are two major reasons for this requirement: (1) composite materials are formed at the time the structure is fabricated and (2) at practical strain levels damage, changes in the condition of the material, that influence the structure's mechanical performance is present. The fundamental basis of such a nondestructive evaluation capability is presented. A discussion of means of assessing nondestructively the material condition as well as a damage mechanics theory that interprets the material condition in terms of its influence on the mechanical response, stiffness, strength and life is provided.

Duke, J. C., Jr.; Henneke, E. G., II; Stinchcomb, W. W.; Reifsnider, K. L.

1984-01-01

187

Reflection and transmission for layered composite materials  

NASA Technical Reports Server (NTRS)

A layered planar structure consisting of different bianisotropic materials separated by jump-immittance sheets is considered. Reflection and transmission coefficients are determined via a chain-matrix algorithm. Applications are important for radomes and radar-absorbing materials.

Graglia, Roberto D.; Uslenghi, Piergiorgio L. E.

1991-01-01

188

Multilayer composite material and method for evaporative cooling  

NASA Technical Reports Server (NTRS)

A multilayer composite material and method for evaporative cooling of a person employs an evaporative cooling liquid that changes phase from a liquid to a gaseous state to absorb thermal energy. The evaporative cooling liquid is absorbed into a superabsorbent material enclosed within the multilayer composite material. The multilayer composite material has a high percentage of the evaporative cooling liquid in the matrix. The cooling effect can be sustained for an extended period of time because of the high percentage of phase change liquid that can be absorbed into the superabsorbent. Such a composite can be used for cooling febrile patients by evaporative cooling as the evaporative cooling liquid in the matrix changes from a liquid to a gaseous state to absorb thermal energy. The composite can be made with a perforated barrier material around the outside to regulate the evaporation rate of the phase change liquid. Alternatively, the composite can be made with an imperveous barrier material or semipermeable membrane on one side to prevent the liquid from contacting the person's skin. The evaporative cooling liquid in the matrix can be recharged by soaking the material in the liquid. The multilayer composite material can be fashioned into blankets, garments and other articles.

Buckley, Theresa M. (Inventor)

2002-01-01

189

Regional Patterns in the Isotopic Composition of Natural and  

E-print Network

Mobilization of natural nitrate (NO3 -) deposits in the subsoil by irrigation water in arid and semiaridRegional Patterns in the Isotopic Composition of Natural and Anthropogenic Nitrate in Groundwater variation in soils, vegetation, topography, and moisture conditions. Introduction Nitrate (NO3 -) is one

190

Scattering loss in electro-optic particulate composite materials  

E-print Network

The effective permittivity dyadic of a composite material containing particulate constituent materials with one constituent having the ability to display the Pockels effect is computed, using an extended version of the strong-permittivity-fluctuation theory which takes account of both the distributional statistics of the constituent particles and their sizes. Scattering loss, thereby incorporated in the effective electromagnetic response of the homogenized composite material, is significantly affected by the application of a low-frequency (dc) electric field.

MacKay, T G; Mackay, Tom G.; Lakhtakia, Akhlesh

2007-01-01

191

LDEF fiber-composite materials characterization  

NASA Technical Reports Server (NTRS)

Degradation of a number of fiber/polymer composites located on the leading and trailing surfaces of LDEF where the atomic oxygen (AO) fluences ranged from 10(exp 22) to 10(exp 4) atoms/cm(sup 2), respectively, was observed and compared. While matrices of the composites on the leading edge generally exhibited considerable degradation and erosion-induced fragmentation, this 'asking' process was confined to the near surface regions because these degraded structures acted as a 'protective blanket' for deeper-lying regions. This finding leads to the conclusion that simple surface coatings can significantly retard AO and other combinations of degrading phenomena in low-Earth orbit. Micrometeoroid and debris particle impacts were not a prominent feature on the fiber composites studied and apparently do not contribute in a significant way to their degradation or alteration in low-Earth orbit.

Miglionico, C. J.; Stein, C.; Roybal, R. E.; Murr, L. E.

1993-01-01

192

Flexible composite material with phase change thermal storage  

NASA Technical Reports Server (NTRS)

A highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The composite material can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The composite may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the PCM composite also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

Buckley, Theresa M. (Inventor)

1999-01-01

193

Flexible composite material with phase change thermal storage  

NASA Technical Reports Server (NTRS)

A highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The composite material can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The composite may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the PCM composite also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, ,gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

Buckley, Theresa M. (Inventor)

2001-01-01

194

Properties of rigid-line inclusions as building blocks of naturally occurring composites  

Microsoft Academic Search

In the present work, rigid-line inclusions (also known as anticracks) are studied as a potential tool for the modelling of building blocks in naturally occurring composites. The choice of rigid-line inclusions is motivated by observations that the mineral phase in such composites as nacre, enamel, and silk consists of inclusions that have a flat plate-like shape and material properties that

Pawan Pingle; James Sherwood; Larissa Gorbatikh

2008-01-01

195

Damage detection in composite materials by FBGs  

NASA Astrophysics Data System (ADS)

Embedded fiber Bragg gratings (FBGs) are sensitive to changes of near strain fields in a composite host monolithic structure, typical of aircraft airframes. FBGs have been embedded in different configurations (a typical position is the skin -- stiffener interface in a monolithic structure) for detecting events associated to damage occurrence. Thus, it is possible to think in FBGs not only as strain sensors, in a classical load monitoring configuration, but as a part of a structural health monitoring (SHM) system in composite structures dimensioned following damage tolerance criteria.

Menendez, Jose M.; Munoz, Pedro; Pintado, J. M.; Guemes, Alfredo

2004-06-01

196

Thermal expansion behaviour of thermoplastic composite materials  

SciTech Connect

The thermal expansion behavior of a number of commercially available and experimental continuous fiber-reinforced PEEK composites is assessed. The thermal expansion characteristics of Hercules AS4 reinforced PEEK (APC-2/AS4, ICI Fiberite) are reported in some detail, and it is shown that behavior is both reasonable and predictable. Further, it is found that repeated thermal cycling between -160 C and +120 C has no effect on the behavior of unidirectional laminates, and that the inherent characteristics of the composite are likely to promote such insensitivity. 16 refs.

Barnes, J.A.; Simms, I.J.; Farrow, G.J.; Jackson, D.; Wostenholm, G. (Imperial Chemical Industries, PLC, Materials Research Centre, Wilton (England) Salford Univ. (England))

1990-01-01

197

Deformation and failure information from composite materials via acoustic emission  

NASA Technical Reports Server (NTRS)

The paper reviews some principles of applying acoustic emission (AE) to the study of fiber-composite materials and structures. This review covers the basics of using AE to monitor the deformation and fracture processes that occur when fiber-composite materials are stressed. Also, new results in some areas of current research interest are presented. The following areas are emphasized: study of couplants for AE testing of composites, evaluation of a special immersion-type AE transducer, and wave propagation complications and the development of techniques for locating AE sources in Kevlar 49/epoxy composite pre

Hamstad, M. A.

1978-01-01

198

Composite nature of the ? (1520) resonance  

NASA Astrophysics Data System (ADS)

Recently, the Weinberg compositeness condition of a bound state was generalized to account for resonant states and higher partial waves. We apply this extension to the case of the ? (1520) resonance and quantify the weight of the meson-baryon components in contrast to other possible genuine building blocks. This resonance was theoretically obtained from a coupled channels analysis using the s-wave ??* and K? * and the d-wave K¯N and ?? channels, applying the techniques of the chiral unitary approach. We obtain the result that this resonance is essentially dynamically generated from these meson-baryon channels, leaving room for only 15% weight of other kinds of components in its wave function.

Aceti, F.; Oset, E.; Roca, L.

2014-08-01

199

Performance of Hemp-Fibre Reinforced Polypropylene Composite Materials.  

E-print Network

??Increasing worldwide environmental awareness is encouraging scientific research into the development of cheaper, more environmentally friendly and more sustainable construction and packaging materials. Natural fibre… (more)

Beckermann, Gareth

2007-01-01

200

Two-dimensional optimization of material composition of functionally graded materials using meshless analyses  

E-print Network

Two-dimensional optimization of material composition of functionally graded materials using-dimensional simulation and optimization of material distribution of functionally graded materials for thermomechanical processes. The proposed approach focuses on metal/ceramic functionally graded materials, which offer great

Vel, Senthil

201

Prediction of natural frequency variability due to uncertainty in material properties  

NASA Technical Reports Server (NTRS)

Composite materials are widely used in various types of modern engineering structures. Traditional studies on composite structures have been based on the assumption that the material properties of the composites are characterized by a priori known elastic moduli, and no uncertainties of these moduli have been considered. However, the composite materials are invariably subject to a certain amount of scatter in their measured elastic moduli. To a large extent, the properties of composite materials are dependent on the fabrication process. But even the composite materials manufactured by the same process demonstrate differences in their elastic properties. This paper proposes a new, non-probabilistic method to predict the variability in the natural frequencies of the composite cylindrical shell, resulting from the unavoidable scatter in elastic moduli. The available measurements of elastic moduli are fitted by the four-dimensional uncertainty ellipsoid. The upper and lower bounds of the natural frequency are derived. With these bounds, designers will have a better understanding of the real dynamic behavior of the structure.

Li, Y. W.

1994-01-01

202

Bone substitute material on the basis of natural components  

NASA Astrophysics Data System (ADS)

The creation of regenerative materials remains a problem for rehabilitation medicine, but the obtaining of initial substances that can cause bone tissue regeneration, possessing biological activity and creation on their basis of composite materials with specified physical and mechanical characteristics is an important scientific problem. This paper presents the investigation of physical-chemical and biological properties of bioresorbable composite material that can restore their own bone tissue of the body.

Melnikova, S.; Zelichenko, E.; Zenin, B.; Guzeev, V.; Gurova, O.

2014-10-01

203

Composite-Material Tanks with Chemically Resistant Liners  

NASA Technical Reports Server (NTRS)

Lightweight composite-material tanks with chemically resistant liners have been developed for storage of chemically reactive and/or unstable fluids . especially hydrogen peroxide. These tanks are similar, in some respects, to the ones described in gLightweight Composite-Material Tanks for Cryogenic Liquids h (MFS-31379), NASA Tech Briefs, Vol. 25, No. 1 (January, 2001), page 58; however, the present tanks are fabricated by a different procedure and they do not incorporate insulation that would be needed to prevent boil-off of cryogenic fluids. The manufacture of a tank of this type begins with the fabrication of a reusable multisegmented aluminum mandrel in the shape and size of the desired interior volume. One or more segments of the mandrel can be aluminum bosses that will be incorporated into the tank as end fittings. The mandrel is coated with a mold-release material. The mandrel is then heated to a temperature of about 400 F (approximately equal to 200 C) and coated with a thermoplastic liner material to the desired thickness [typically approxiamtely equal to 15 mils (approximately equal to 0.38 mm)] by thermal spraying. In the thermal-spraying process, the liner material in powder form is sprayed and heated to the melting temperature by a propane torch and the molten particles land on the mandrel. The sprayed liner and mandrel are allowed to cool, then the outer surface of the liner is chemically and/or mechanically etched to enhance bonding of a composite overwrap. The etched liner is wrapped with multiple layers of an epoxy resin reinforced with graphite fibers; the wrapping can be done either by manual application of epoxy-impregnated graphite cloth or by winding of epoxy-impregnated filaments. The entire assembly is heated in an autoclave to cure the epoxy. After the curing process, the multisegmented mandrel is disassembled and removed from inside, leaving the finished tank. If the tank is to be used for storing hydrogen peroxide, then the liner material should be fluorinated ethylene/propylene (FEP), and one or more FEP O ring(s) should be used in the aluminum end fitting(s). This choice of materials is dictated by experimental observations that pure aluminum and FEP are the only materials suitable for long-term storage of hydrogen peroxide and that other materials tend to catalyze the decomposition of hydrogen peroxide to oxygen and water. Other thermoplastic liner materials that are suitable for some applications include nylon 6 and polyethylene. The processing temperatures for nylon 6 are lower than those for FEP. Nylon 6 is compatible with propane, natural gas, and other petroleum-based fuels. Polyethylene is compatible with petroleum- based products and can be used for short-term storage of hydrogen peroxide.

DeLay, Thomas K.

2004-01-01

204

Solid freeform fabrication of highly loaded composite materials  

NASA Astrophysics Data System (ADS)

Composites are known for their unique blend of modulus, strength, and toughness. This study focuses on two types of composites; organic-inorganic hybrids and the mineralization of highly swollen polymer gels. Both of these composite systems mimic the biological process of composite formation, known as biomineralization. Biomineralization allows for the control of the precipitating phase through an interaction with the organic matrix. This allows higher volume fractions of inorganic material than can be achieved by many traditional processing techniques. Solid freeform fabrication is a processing method that builds materials by the sequential addition of thin layers. As long as the material can easily be converted from a liquid to a solid, it should be amenable for this processing technique. Freeform fabrication has three distinctions from traditional processing techniques that may enable the formation of composite materials with improved mechanical properties. These are the sequential addition of layers, which allows a layer by layer influence of chemistry, the ability to form complex geometries, and finally, extrusion freeform fabrication has been shown to align fibers due to the extrusion of the slurry through a needle. Cracking and shrinkage still play a major role in forming solid parts. The use of an open mesh structure in combination with proper materials selection allowed the formation of highly loaded composite materials without cracking. The modulus values of these materials ranged from 0.1 GPa to 6.0 GPa. The mechanical properties of these materials were modeled.

Souvignier, Chad William

205

Advanced AE Techniques in Composite Materials Research  

NASA Technical Reports Server (NTRS)

Advanced, waveform based acoustic emission (AE) techniques have been successfully used to evaluate damage mechanisms in laboratory testing of composite coupons. An example is presented in which the initiation of transverse matrix cracking was monitored. In these tests, broad band, high fidelity acoustic sensors were used to detect signals which were then digitized and stored for analysis. Analysis techniques were based on plate mode wave propagation characteristics. This approach, more recently referred to as Modal AE, provides an enhanced capability to discriminate and eliminate noise signals from those generated by damage mechanisms. This technique also allows much more precise source location than conventional, threshold crossing arrival time determination techniques. To apply Modal AE concepts to the interpretation of AE on larger composite specimens or structures, the effects of modal wave propagation over larger distances and through structural complexities must be well characterized and understood. To demonstrate these effects, measurements of the far field, peak amplitude attenuation of the extensional and flexural plate mode components of broad band simulated AE signals in large composite panels are discussed. These measurements demonstrated that the flexural mode attenuation is dominated by dispersion effects. Thus, it is significantly affected by the thickness of the composite plate. Furthermore, the flexural mode attenuation can be significantly larger than that of the extensional mode even though its peak amplitude consists of much lower frequency components.

Prosser, William H.

1996-01-01

206

Delamination durability of composite materials for rotorcraft  

NASA Technical Reports Server (NTRS)

Delamination is the most commonly observed failure mode in composite rotorcraft dynamic components. Although delamination may not cause immediate failure of the composite part, it often precipitates component repair or replacement, which inhibits fleet readiness, and results in increased life cycle costs. A fracture mechanics approach for analyzing, characterizing, and designing against delamination will be outlined. Examples of delamination problems will be illustrated where the strain energy release rate associated with delamination growth was found to be a useful generic parameter, independent of thickness, layup, and delamination source, for characterizing delamination failure. Several analysis techniques for calculating strain energy release rates for delamination from a variety of sources will be outlined. Current efforts to develop ASTM standard test methods for measuring interlaminar fracture toughness and developing delamination failure criteria will be reviewed. A technique for quantifying delamination durability due to cyclic loading will be presented. The use of this technique for predicting fatigue life of composite laminates and developing a fatigue design philosophy for composite structural components will be reviewed.

Obrien, T. Kevin

1988-01-01

207

LIGNOCELLULOSIC-PLASTIC COMPOSITES FROM RECYCLED MATERIALS  

EPA Science Inventory

Waste wood, waste paper, and waste plastics are major components of MSW and offer great opportunities as recycled ingredients in wood-fiber plastic composites. USEPA and the USDA Forest Products Laboratory (FPL) are collaborating on a research project to investigate the processin...

208

Advanced composites: Fabrication processes for selected resin matrix materials  

NASA Technical Reports Server (NTRS)

This design note is based on present state of the art for epoxy and polyimide matrix composite fabrication technology. Boron/epoxy and polyimide and graphite/epoxy and polyimide structural parts can be successfully fabricated. Fabrication cycles for polyimide matrix composites have been shortened to near epoxy cycle times. Nondestructive testing has proven useful in detecting defects and anomalies in composite structure elements. Fabrication methods and tooling materials are discussed along with the advantages and disadvantages of different tooling materials. Types of honeycomb core, material costs and fabrication methods are shown in table form for comparison. Fabrication limits based on tooling size, pressure capabilities and various machining operations are also discussed.

Welhart, E. K.

1976-01-01

209

Preparation of composite materials in space. Volume 2: Technical report  

NASA Technical Reports Server (NTRS)

A study to define promising materials, significant processing criteria, and the related processing techniques and apparatus for the preparation of composite materials in space was conducted. The study also established a program for zero gravity experiments and the required developmental efforts. The following composite types were considered: (1) metal-base fiber and particle composites, including cemented compacts, (2) controlled density metals, comprising plain and reinforced metal foams, and (3) unidirectionally solidified eutectic alloys. A program of suborbital and orbital experiments for the 1972 to 1978 time period was established to identify materials, processes, and required experiment equipment.

Steurer, W. H.; Kaye, S.

1973-01-01

210

Composite metal foil and ceramic fabric materials  

DOEpatents

The invention comprises new materials useful in a wide variety of terrestrial and space applications. In one aspect, the invention comprises a flexible cloth-like material comprising a layer of flexible woven ceramic fabric bonded with a layer of metallic foil. In another aspect, the invention includes a flexible fluid impermeable barrier comprising a flexible woven ceramic fabric layer having metal wire woven therein. A metallic foil layer is incontinuously welded to the woven metal wire. In yet another aspect, the invention includes a material comprising a layer of flexible woven ceramic fabric bonded with a layer of an organic polymer. In still another aspect, the invention includes a rigid fabric structure comprising a flexible woven ceramic fabric and a resinous support material which has been hardened as the direct result of exposure to ultraviolet light. Inventive methods for producing such material are also disclosed.

Webb, Brent J. (Richland, WA); Antoniak, Zen I. (Richland, WA); Prater, John T. (Chapel Hill, NC); DeSteese, John G. (Kennewick, WA)

1992-01-01

211

Microbiological destruction of composite polymeric materials in soils  

NASA Astrophysics Data System (ADS)

Representatives of the same species of microscopic fungi developed on composite materials with similar polymeric matrices independently from the type of soils, in which the incubation was performed. Trichoderma harzianum, Penicillium auranthiogriseum, and Clonostachys solani were isolated from the samples of polyurethane. Fusarium solani, Clonostachys rosea, and Trichoderma harzianum predominated on the surface of ultrathene samples. Ulocladium botrytis, Penicillium auranthiogriseum, and Fusarium solani predominated in the variants with polyamide. Trichoderma harzianum, Penicillium chrysogenum, Aspergillus ochraceus, and Acremonium strictum were isolated from Lentex-based composite materials. Mucor circinelloides, Trichoderma harzianum, and Penicillium auranthiogriseum were isolated from composite materials based on polyvinyl alcohol. Electron microscopy demonstrated changes in the structure of polymer surface (loosening and an increase in porosity) under the impact of fungi. The physicochemical properties of polymers, including their strength, also changed. The following substances were identified as primary products of the destruction of composite materials: stearic acid for polyurethane-based materials; imide of dithiocarbonic acid and 1-nonadecen in variants with ultrathene; and tetraaminopyrimidine and isocyanatodecan in variants with polyamide. N,N-dimethyldodecan amide, 2-methyloximundecanon and 2-nonacosane were identified for composites on the base of Lentex A4-1. Allyl methyl sulfide and imide of dithiocarbonic acid were found in variants with the samples of composites based on polyvinyl alcohol. The identified primary products of the destruction of composite materials belong to nontoxic compounds.

Legonkova, O. A.; Selitskaya, O. V.

2009-01-01

212

NATURE MATERIALS | VOL 10 | NOVEMBER 2011 | www.nature.com/naturematerials 817 requirement for almost all engineering structural materials  

E-print Network

NATURE MATERIALS | VOL 10 | NOVEMBER 2011 | www.nature.com/naturematerials 817 A requirement for almost all engineering structural materials is that they are both strong and tough (damage tolerant) yet invariably, in most materials, the properties of strength and toughness are mutually exclusive

Ritchie, Robert

213

Proc ACUN-5 "Developments in Composites: Advanced, Infrastructural, Natural and Nano-compsoites", UNSW, SYDNEY, Australia,  

E-print Network

Proc ACUN-5 "Developments in Composites: Advanced, Infrastructural, Natural and Nano-compsoites", UNSW, SYDNEY, Australia, 11-14 July 2006 High modulus carbon fiber materials for retrofit of steel_rizkalla@ncsu.edu Abstract This paper summarizes the research work dealing with the use of high modulus carbon fiber

214

The atomic weight and isotopic composition of boron and their variation in nature  

SciTech Connect

The boron isotopic composition and atomic weight value and their variation in nature are reviewed. Questions are raised about the previously recommended value and the uncertainty for the atomic weight. The problem of what constitutes an acceptable range for normal material and what should then be considered geologically exceptional is discussed. Recent measurements make some previous decisions in need of re-evaluation.

Holden, N.E.

1993-08-01

215

Influence of thermal aging on crosslinking density of boron carbide\\/natural rubber composites  

Microsoft Academic Search

Composites of natural rubber and boron carbide with different concentrations were prepared as thermal neutron radiation shielding materials. The maximum degree of swelling (Q), the penetration rate (P) and the average diffusion coefficient (Dav) were studied. Using the Flory–Rehner equation, the crosslinking densities of the investigated samples were obtained. The effect of thermal oxidative aging on both the swelling behaviour

S. E. Gwaily; M. M. Badawy; H. H. Hassan; M. Madani

2003-01-01

216

Machine augmented composite materials for damping purposes  

E-print Network

are formed by inserting simple machines into a matrix material. In this work the machines take the form of fluid filled tubes, and the tube cross-sectional geometry induces fluid flow when it is deformed in its plane. This flow dissipates mechanical... to the product of the driving frequency and the fluid dynamic viscosity. This is a measure of the ratio of elastic forces in the solid material to the viscous forces in the fluid material that makes up a MAC lamina. Governing equations and simulation methods...

McCutcheon, David Matthew

2005-02-17

217

Electrical Characterizations of Lightning Strike Protection Techniques for Composite Materials  

NASA Technical Reports Server (NTRS)

The growing application of composite materials in commercial aircraft manufacturing has significantly increased the risk of aircraft damage from lightning strikes. Composite aircraft designs require new mitigation strategies and engineering practices to maintain the same level of safety and protection as achieved by conductive aluminum skinned aircraft. Researchers working under the NASA Aviation Safety Program s Integrated Vehicle Health Management (IVHM) Project are investigating lightning damage on composite materials to support the development of new mitigation, diagnosis & prognosis techniques to overcome the increased challenges associated with lightning protection on composite aircraft. This paper provides an overview of the electrical characterizations being performed to support IVHM lightning damage diagnosis research on composite materials at the NASA Langley Research Center.

Szatkowski, George N.; Nguyen, Truong X.; Koppen, Sandra V.; Ely, Jay J.; Mielnik, John J.

2009-01-01

218

Characterization of thermoplastic polyamide composite matrix material  

SciTech Connect

The research described here involves a study for a representative matrix resin, the J1-polymer (a polyamide) proposed by DuPont. The research was conducted in parallel with related studies, primarily by other personnel, of graphite fiber/J1-polymer unidirectional composites. X-ray and transmission electron microscopy studies were conducted to examine the structure/morphology of the neat resin. Thermal analysis by differential scanning calorimetry was used to investigate the effects of different heating and cooling rates and various processing conditions. Dynamic mechanical properties of the neat resin were characterized. The fundamental mechanisms of deformation and failure, including creep, crack growth and fracture behaviors, were examined both at room temperature and at elevated temperature. A number of the techniques were extended to characterize the composite as well as the neat resin.

Chen, W.L.A.

1987-01-01

219

Photorefractivity in liquid crystalline composite materials  

SciTech Connect

We report recent improvements in the photorefractive of liquid crystalline thin film composites containing electron donor and acceptor molecules. The improvements primarily result from optimization of the exothermicity of the intermolecular charge transfer reaction and improvement of the diffusion characteristics of the photogenerated ions. Intramolecular charge transfer dopants produce greater photorefractivity and a 10-fold decrease in the concentration of absorbing chromophores. The mechanism for the generation of mobile ions is discussed.

Wiederrecht, G.P. [Argonne National Lab., IL (United States); Wasielewski, M.R. [Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry

1997-09-01

220

Digital cellular solids : reconfigurable composite materials  

E-print Network

Digital materials are comprised of a small number of types of discrete physical building blocks, which assemble to form constructions that meet the versatility and scalability of digital computation and communication ...

Cheung, Kenneth Chun-Wai

2012-01-01

221

Sulphidation resistance of composite boiler tube materials  

SciTech Connect

A lab-based testing program was undertaken to generate data to better define the sulphidation resistance of composite tubes installed in the lower-furnace section of black liquor recovery boilers. All composite tube cladding alloys tested were observed to have an acceptable corrosion rate at normal operating temperatures (up to 400 C) in the synthetic lower-furnace gaseous environment tested (1% H{sub 2}S-99% N{sub 2}). This acceptable corrosion resistance is due to the expected formation of a relatively protective chromium-rich inner sulphide scale. An increase in temperature up to 560 C was found to significantly increase the corrosion rate. Of the various alloys tested, Alloy HR11N exhibited the lowest corrosion rate at each of the three temperatures tested. Moreover, the corrosion rate was found not to be strongly dependent on the fabrication route (weld overlay versus co-extruded). To minimize corrosion, operating conditions that promote prolonged exposure to elevated temperatures in the lower-furnace section of black liquor recovery boilers should be avoided, regardless of the type of composite tube installed.

Kish, Joseph [McMaster University; Eng, Philip [FPInnovations; Singbeil, Douglas [FPInnovations; Keiser, James R [ORNL

2008-01-01

222

Metal oxide composite dosimeter method and material  

DOEpatents

The present invention is a method of measuring a radiation dose wherein a radiation responsive material consisting essentially of metal oxide is first exposed to ionizing radiation. The metal oxide is then stimulating with light thereby causing the radiation responsive material to photoluminesce. Photons emitted from the metal oxide as a result of photoluminescence may be counted to provide a measure of the ionizing radiation.

Miller, Steven D. (Richland, WA)

1998-01-01

223

Alternative methods for determination of composition and porosity in abradable materials  

SciTech Connect

Materials properties and performance are governed by their composition and structure. These are commonly characterized using materialography and image analysis. However, in abradable materials, obtaining a reliable and representative sample (polished section) for this widespread technique is complicated by their abradable nature and heterogeneity. Therefore, alternative methods are also considered in this paper. They are namely X-ray diffraction and electron probe microanalysis to determine the composition, and mercury intrusion porosimetry, Archimedean porosimetry and helium pycnometry to determine the porosity. These methods, including materialography, were applied on representative abradable materials produced by plasma spraying; their results are compared and the advantages and drawbacks of each method are discussed.

Matejicek, Jiri [Institute of Plasma Physics, Za Slovankou 3, 18200 Praha 8, Prague (Czech Republic)]. E-mail: jmatejic@ipp.cas.cz; Kolman, Blahoslav [Institute of Plasma Physics, Za Slovankou 3, 18200 Praha 8, Prague (Czech Republic); Dubsky, Jiri [Institute of Plasma Physics, Za Slovankou 3, 18200 Praha 8, Prague (Czech Republic); Neufuss, Karel [Institute of Plasma Physics, Za Slovankou 3, 18200 Praha 8, Prague (Czech Republic); Hopkins, Noel [Rolls-Royce, PO Box 31, Derby DE24 8BJ (United Kingdom); Zwick, Jochen [Institut fuer Oberflaechentechnik, RWTH, Templergraben 55, 52062 Aachen (Germany)

2006-07-15

224

Material Delivery System for Aircraft Composite Component Manufacturing Workshop  

E-print Network

Abstract—This paper presents a material delivery system for the aircraft composite component manufacturing workshop. By analyzing the disadvantages of the passive material supply model, an active material delivery model is proposed. Subsequently, an improved work flow of material delivery is introduced in detail for optimizing the traditional material supply. Barcode technology is used to collect the data of material receiving and issuing in the warehouse. By scanning the barcode, material information and working personnel information can be collected and inputted into the system in real time. The function module of material delivery system is composed of material delivery management, inventory management, and production planning management. The integration relationship between the material delivery system and other systems is also described. Three-layer structure is adopted to design and develop the system. The material delivery system has been implemented in an aircraft composite component manufacturing workshop. The results show that material supply time and cost has been reduced. Index Terms—material delivery, composite component, MES, barcode

Mei Zhongyi; Liu Yongjin; Muhammad Younus

225

Health, safety and environmental requirements for composite materials  

NASA Technical Reports Server (NTRS)

The health, safety and environmental requirements for the production of composite materials are discussed. The areas covered include: (1) chemical identification for each chemical; (2) toxicology; (3) industrial hygiene; (4) fire and safety; (5) environmental aspects; and (6) medical concerns.

Hazer, Kathleen A.

1994-01-01

226

Nondestructive testing of polymer composite materials using THz radiation  

NASA Astrophysics Data System (ADS)

This paper shows an ability to find internal defects in construction of polymer composite material using THz imaging. Using THz vision system resulted in an example of finding internal non-impregnated area in fiberglass.

Yakovlev, Egor V.; Zaytsev, Kirill I.; Fokina, Irina N.; Karasik, Valeriy E.; Yurchenko, Stanislav O.

2014-03-01

227

Flight service environmental effects on composite materials and structures  

NASA Technical Reports Server (NTRS)

NASA Langley and the U.S. Army have jointly sponsored programs to assess the effects of realistic flight environments and ground-based exposure on advanced composite materials and structures. Composite secondary structural components were initially installed on commercial transport aircraft in 1973; secondary and primary structural components were installed on commercial helicopters in 1979; and primary structural components were installed on commercial aircraft in the mid-to-late 1980's. Service performance, maintenance characteristics, and residual strength of numerous components are reported. In addition to data on flight components, 10 year ground exposure test results on material coupons are reported. Comparison between ground and flight environmental effects for several composite material systems are also presented. Test results indicate excellent in-service performance with the composite components during the 15 year period. Good correlation between ground-based material performance and operational structural performance has been achieved.

Dexter, H. Benson; Baker, Donald J.

1992-01-01

228

The Natural Materials Browser: Using a Tablet Interface for Exploring Volumetric Materials Science Datasets  

E-print Network

The Natural Materials Browser: Using a Tablet Interface for Exploring Volumetric Materials Science angus.forbes@sista.arizona.edu Tony Fast Department of Materials Science Georgia Institute of Technology Barbara holl@cs.ucsb.edu ABSTRACT We present a novel tablet application, the Natural Materials Browser

Hollerer, Tobias

229

ENG 4793: Composite Materials and Processes 1 Combining Thermoplastics with  

E-print Network

1 ENG 4793: Composite Materials and Processes 1 Combining Thermoplastics with Reinforcing Fibers and Processes 7 Short Fiber Processes Thermoplastic Pellets Chopped Fibers Extruder Strand Die Water Bath Pellets Cooler Rovings Thermoplastic Pellets Counter Flow Die ( USP 5,176,775 ) #12;3 ENG 4793: Composite

Colton, Jonathan S.

230

Composite materials based on wastes of flat glass processing  

Microsoft Academic Search

Glass mirrors scrap and poly (vinyl) butiral waste (PVB) obtained from flat glass processing plants were investigated as raw materials to produce composites. The emphasis was on studying the influence of milled glass mirror waste contents on properties of composites produced with PVB. The characterization involved: elongation under rupture, water absorption, tensile strength and elastic modulus tests. The results showed

A. V. Gorokhovsky; J. I. Escalante-Garcia; G. Yu. Gashnikova; L. P. Nikulina; S. E. Artemenko

2005-01-01

231

Structurally integrated fiber optic damage assessment system for composite materials  

Microsoft Academic Search

Progress toward the development of a fiber optic damage assessment system for composite materials is reported. This system, based on the fracture of embedded optical fibers, has been characterized with respect to the orientation and location of the optical fibers in the composite. Together with a special treatment, these parameters have been tailored to yield a system capable of detecting

N. D. W. Glossop; J. Lymer; M. Leblanc; S. Dubois; W. Tsaw; R. C. Tennyson

1989-01-01

232

A physically-based abrasive wear model for composite materials  

Microsoft Academic Search

A simple physically-based model for the abrasive wear of composite materials is presented based on the mechanics and mechanisms associated with sliding wear in soft (ductile)- matrix composites containing hard (brittle) reinforcement particles. The model is based on the assumption that any portion of the reinforcement that is removed as wear debris cannot contribute to the wear resistance of the

Gun Y. Lee; C. K. H. Dharan; R. O. Ritchie

2002-01-01

233

A physically-based abrasive wear model for composite materials  

Microsoft Academic Search

A simple physically-based model for the abrasive wear of composite materials is presented based on the mechanics and mechanisms associated with sliding wear in soft (ductile) matrix composites containing hard (brittle) reinforcement particles. The model is based on the assumption that any portion of the reinforcement that is removed as wear debris cannot contribute to the wear resistance of the

Gun Y. Lee; C. K. H. Dharan; Robert O. Ritchie

2001-01-01

234

Polymer?Nanoparticle Composites: Preparative Methods and Electronically Active Materials  

Microsoft Academic Search

The field of nanoparticle?polymer composites is attractive from the standpoint of integrating the key features of both polymers and nanoparticles into hybrid or composite materials. Nanocomposites geared towards electronic and photophysical targets comprise an intriguing subset of the field, and benefit from interdisciplinary efforts in nanoparticle and polymer synthesis, along with methodology that provides the dispersion, orientation, and\\/or the assembly

P. K. Sudeep; Todd Emrick

2007-01-01

235

Leaching of technologically enhanced naturally occurring radioactive materials.  

PubMed

A form of waste associated with mining activities is related to the type of deposit being mined and to the procedure of exploitation and enrichment adopted. The wastes usually contain relatively large amounts of technologically enhanced naturally occurring radioactive materials (TENORM). The TENORM are often stored on the surface. Consequently, they can be leached as a result of interaction with aqueous solutions of different chemical composition. This further leads to pollution of water and soil in the vicinity of the stored wastes. The paper presents the results of laboratory investigation aimed at quantifying the leaching process of samples originating from uranium dumps and storage reservoirs associated with brine pumped from coal mines. The leaching process was investigated with respect to selected elements: uranium isotopes, radium isotopes, iron, barium and sodium. The samples were exposed to aqueous solutions of different chemical composition. The experiments revealed that TENORM in form of sulphate compounds are the most resistant against leaching. The leaching coefficient for radium isotopes varies from a few thousandth percent to a few hundredth percent. On the other hand, for TENORM occurring in sand or sludge, the leaching coefficient for uranium and radium isotopes ranged from a few hundredth percent to a few percent. PMID:17482828

Chau, Nguyen Dinh; Chru?ciel, Edward

2007-08-01

236

Magnetic-marker system using ferrite composite materials  

SciTech Connect

The author`s group has developed some new ferrite composite materials by mixing ferrite by-products with binders such as cement, asphalt cement and epoxy resin. The authors have also developed a magnetic marker sensing system consisting of the ferrite composite material used as a magnetic marker embedded in an asphalt pavement or other surface and a portable magnetic sensor. This system has been applied in a guide lane for the blind and in a speed meter for a motor vehicle.

Mayama, Masakazu [Hokkaido Institute of Technology, Sapporo (Japan)

1993-12-31

237

Teaching Composition in Prisons: Methods and Materials.  

ERIC Educational Resources Information Center

A pilot study gathered information on materials and methods used by writing instructors teaching in prisons in Tennessee, Kentucky, Illinois, and Missouri via a questionnaire. The classes taught by the respondents were all at the college level, were sponsored by various universities and colleges, and all but two were taught at maximum security…

Mowery, Carl D., Jr.

238

Coplanar circulator made from composite magnetic material  

Microsoft Academic Search

This paper deals with the operation of a Y- junction coplanar circulator. It operates at high frequencies (>40 GHz). Barium hexaferrite particles within a host matrix form the integrated magnetic material in this device. The structure of this 3-port microwave device and its different characteristics are presented. A three dimensional finite element method was used to calculate the S-parameters and

Taline Boyajian; Didier Vincent; Sophie Neveu; Martine LeBerre; Jean-Jacques Rousseau

2011-01-01

239

Viscoelastic models for polymeric composite materials  

Microsoft Academic Search

An improved model of the mechanical properties of the explosive contained in conventional munitions is needed to accurately simulate performance and accident scenarios in weapons storage facilities. A specific class of explosives can be idealized as a mixture of two components: energetic crystals randomly suspended in a polymeric matrix (binder). Strength characteristics of each component material are important in the

S. G. Bardenhagen; E. N. Harstad; J. C. Jr. Foster; P. J. Maudlin

1996-01-01

240

Composite Structures and Materials Research at NASA Langley Research Center  

NASA Technical Reports Server (NTRS)

A summary of recent composite structures and materials research at NASA Langley Research Center is presented. Fabrication research to develop low-cost automated robotic fabrication procedures for thermosetting and thermoplastic composite materials, and low-cost liquid molding processes for preformed textile materials is described. Robotic fabrication procedures discussed include ply-by-ply, cure-on-the-fly heated placement head and out-of-autoclave electron-beam cure methods for tow and tape thermosetting and thermoplastic materials. Liquid molding fabrication processes described include Resin Film Infusion (RFI), Resin Transfer Molding (RTM) and Vacuum-Assisted Resin Transfer Molding (VARTM). Results for a full-scale composite wing box are summarized to identify the performance of materials and structures fabricated with these low-cost fabrication methods.

Starnes, James H., Jr.; Dexter, H. Benson; Johnston, Norman J.; Ambur, Damodar R.; Cano, roberto J.

2003-01-01

241

Composite Structures and Materials Research at NASA Langley Research Center  

NASA Technical Reports Server (NTRS)

A summary of recent composite structures and materials research at NASA Langley Research Center is presented. Fabrication research to develop low-cost automated robotic fabrication procedures for thermosetting and thermoplastic composite materials, and low-cost liquid molding processes for preformed textile materials is described. Robotic fabrication procedures discussed include ply-by-ply, cure-on-the-fly heated placement head and out-of-autoclave electron-beam cure methods for tow and tape thermosetting and thermoplastic materials. Liquid molding fabrication processes described include Resin Film Infusion (RFI) Resin Transfer Molding (RTM) and Vacuum-Assisted Resin Transfer Molding (VARTM). Results for a full-scale composite wing box are summarized to identify the performance of materials and structures fabricated with these low-cost fabrication methods.

Starnes, James H., Jr.; Dexter, H. Benson; Johnston, Norman J.; Ambur, Damodar R.; Cano, Roberto J.

2001-01-01

242

Method and apparatus for gripping uniaxial fibrous composite materials  

NASA Technical Reports Server (NTRS)

A strip specimen is cut from a unidirectional strong, brittle fiber composite material, and the surfaces of both ends of the specimen are grit blasted. The specimen is then placed between metal load transfer members having grit blasted surfaces. Sufficient compressive stress is applied to the load transfer members to prevent slippage during testing at both elevated temperatures and room temperatures. The need for adhesives, load pads, and other secondary composite processing is eliminated. This gripping system was successful in tensile testing, creep rupture testing, and fatigue testing uniaxial composite materials at 316 C.

Whittenberger, J. D.; Hurwitz, F. I. (inventors)

1984-01-01

243

Composition and process for making an insulating refractory material  

DOEpatents

A composition and process are disclosed for making an insulating refractory material. The composition includes calcined alumina powder, flash activated alumina powder, an organic polymeric binder and a liquid vehicle which is preferably water. Starch or modified starch may also be added. A preferred insulating refractory material made with the composition has a density of about 2.4--2.6 g/cm{sup 3} with reduced thermal conductivity, compared with tabular alumina. Of importance, the formulation has good abrasion resistance and crush strength during intermediate processing (commercial sintering) to attain full strength and refractoriness.

Pearson, A.; Swansiger, T.G.

1998-04-28

244

Composition and process for making an insulating refractory material  

DOEpatents

A composition and process for making an insulating refractory material. The composition includes calcined alumina powder, flash activated alumina powder, an organic polymeric binder and a liquid vehicle which is preferably water. Starch or modified starch may also be added. A preferred insulating refractory material made with the composition has a density of about 2.4-2.6 g/cm.sup.3 with reduced thermal conductivity, compared with tabular alumina. Of importance, the formulation has good abrasion resistance and crush strength during intermediate processing (commercial sintering) to attain full strength and refractoriness, good abrasion resistance and crush strength.

Pearson, Alan (Murrysville, PA); Swansiger, Thomas G. (Apollo, PA)

1998-04-28

245

Composition/bandgap selective dry photochemical etching of semiconductor materials  

DOEpatents

Disclosed is a method of selectively photochemically dry etching a first semiconductor material of a given composition and direct bandgap Eg/sub 1/ in the presence of a second semiconductor material of a different composition and direct bandgap Eg/sub 2/, wherein Eg/sub 2/ > Eg/sub 1/, said second semiconductor material substantially not being etched during said method. The method comprises subjecting both materials to the same photon flux and to the same gaseous etchant under conditions where said etchant would be ineffective for chemical etching of either material were the photons not present, said photons being of an energy greater than Eg/sub 1/ but less than Eg/sub 2/, whereby said first semiconductor material is photochemically etched and said second material is substantially not etched.

Ashby, C.I.H.; Dishman, J.L.

1985-10-11

246

Composition/bandgap selective dry photochemical etching of semiconductor materials  

DOEpatents

A method of selectively photochemically dry etching a first semiconductor material of a given composition and direct bandgap Eg.sub.1 in the presence of a second semiconductor material of a different composition and direct bandgap Eg.sub.2, wherein Eg.sub.2 >Eg.sub.1, said second semiconductor material substantially not being etched during said method, comprises subjecting both materials to the same photon flux and to the same gaseous etchant under conditions where said etchant would be ineffective for chemical etching of either material were the photons not present, said photons being of an energy greater than Eg.sub.1 but less than Eg.sub.2, whereby said first semiconductor material is photochemically etched and said second material is substantially not etched.

Ashby, Carol I. H. (Edgewood, NM); Dishman, James L. (Albuquerque, NM)

1987-01-01

247

Carbon Cryogel Silicon Composite Anode Materials for Lithium Ion Batteries  

NASA Technical Reports Server (NTRS)

A variety of materials are under investigation for use as anode materials in lithium-ion batteries, of which, the most promising are those containing silicon. 10 One such material is a composite formed via the dispersion of silicon in a resorcinol-formaldehyde (RF) gel followed by pyrolysis. Two silicon-carbon composite materials, carbon microspheres and nanofoams produced from nano-phase silicon impregnated RF gel precursors have been synthesized and investigated. Carbon microspheres are produced by forming the silicon-containing RF gel into microspheres whereas carbon nano-foams are produced by impregnating carbon fiber paper with the silicon containing RF gel to create a free standing electrode. 1-4,9 Both materials have demonstrated their ability to function as anodes and utilize the silicon present in the material. Stable reversible capacities above 400 mAh/g for the bulk material and above 1000 mAh/g of Si have been observed.

Woodworth James; Baldwin, Richard; Bennett, William

2010-01-01

248

Natural-fiber-reinforced polymer composites in automotive applications  

Microsoft Academic Search

In the past decade, natural-fiber composites with thermoplastic and thermoset matrices have been embraced by European car\\u000a manufacturers and suppliers for door panels, seat backs, headliners, package trays, dashboards, and interior parts. Natural\\u000a fibers such as kenaf, hemp, flax, jute, and sisal offer such benefits as reductions in weight, cost, and CO2, less reliance on foreign oil sources, and recyclability.

James Holbery; Dan Houston

2006-01-01

249

Fracture analysis of composite materials by using photoelastic technique  

SciTech Connect

In this paper analytical equations have been derived for the determination of strain energy density factor (S-factor) and damage energy density factor (Z-factor) in composite materials. Dilatational and distortional energy density factors are discussed. Applications of stress-optical law in composite fracture analysis are studied. Equations to determine stress intensity factors in composite structure by using photoelastic coating techniques are also derived. The technique and equations introduced in this paper can be effectively applied in complicated composite structure for fracture analysis. They are specially useful for solving engineering problems in which no theoretical results are available.

Zhang, S.Q.; Wang, J.; Zu, J.B.; Sun, H.

1993-12-31

250

Accelerated hygrothermal stabilization of composite materials  

SciTech Connect

Experimentation validated a simple moisture conditioning scheme to prepare Gr/Ep composite parts for precision applications by measuring dimensional changes over 90 days. It was shown that an elevated temperature moisture conditioning scheme produced a dimensionally stable part from which precision structures could be built/machined without significant moisture induced dimensional changes after fabrication. Conversely, that unconditioned Gr/Ep composite panels exhibited unacceptably large dimensional changes (i.e., greater than 125 ppM). It was also shown that time required to produce stable parts was shorter, by more than an order of magnitude, employing the conditioning scheme than using no conditioning scheme (46 days versus 1000+ days). Two final use environments were chosen for the experiments: 50% RH/21C and 0% RH/21C. Fiberite 3034K was chosen for its widespread use in aerospace applications. Two typical lay-ups were chosen, one with low sensitivity to hygrothermal distortions and the other high sensitivity: [0, {plus_minus} 45, 90]s, [0, {plus_minus} 15, 0]s. By employing an elevated temperature, constant humidity conditioning scheme, test panels achieved an equilibrium moisture content in less time, by more than an order of magnitude, than panels exposed to the same humidity environment and ambient temperature. Dimensional changes, over 90 days, were up to 4 times lower in the conditioned panels compared to unconditioned panels. Analysis of weight change versus time of test coupons concluded that the out-of-autoclave moisture content of Fiberite 3034K varied between 0.06 and 0.1%.

Gale, J.A.

1994-05-01

251

Lightweight Composite Materials for Heavy Duty Vehicles  

SciTech Connect

The main objective of this project is to develop, analyze and validate data, methodologies and tools that support widespread applications of automotive lightweighting technologies. Two underlying principles are guiding the research efforts towards this objective: • Seamless integration between the lightweight materials selected for certain vehicle systems, cost-effective methods for their design and manufacturing, and practical means to enhance their durability while reducing their Life-Cycle-Costs (LCC). • Smooth migration of the experience and findings accumulated so far at WVU in the areas of designing with lightweight materials, innovative joining concepts and durability predictions, from applications to the area of weight savings for heavy vehicle systems and hydrogen storage tanks, to lightweighting applications of selected systems or assemblies in light–duty vehicles.

Pruez, Jacky; Shoukry, Samir; Williams, Gergis; Shoukry, Mark

2013-08-31

252

Materialism, conspicious consumption and the human nature  

Microsoft Academic Search

By nature, humans are social beings. We are constantly communicating and we interact with many different people in a variety of contexts. Some interactions fulfill an economic function, aimed at exchanging products, while other interactions may have an in- or explicit sexual purpose. Irrespective of the purpose of an interaction, numerous factors may shape its course, outcome, or the way

Inge Lens

2012-01-01

253

Electrospun Nanofiber Coating of Fiber Materials: A Composite Toughening Approach  

NASA Technical Reports Server (NTRS)

Textile-based composites could significantly benefit from local toughening using nanofiber coatings. Nanofibers, thermoplastic or otherwise, can be applied to the surface of the fiber tow bundle, achieving toughening of the fiber tow contact surfaces, resulting in tougher and more damage-resistant/tolerant composite structures. The same technique could also be applied to other technologies such as tape laying, fiber placement, or filament winding operations. Other modifications to the composite properties such as thermal and electrical conductivity could be made through selection of appropriate nanofiber material. Control of the needle electric potential, precursor solution, ambient temperature, ambient humidity, airflow, etc., are used to vary the diameter and nanofiber coating morphology as needed. This method produces a product with a toughening agent applied to the fiber tow or other continuous composite precursor material where it is needed (at interfaces and boundaries) without interfering with other composite processing characteristics.

Kohlman, Lee W.; Roberts, Gary D.

2012-01-01

254

Olivine Composite Cathode Materials for Improved Lithium Ion Battery Performance  

SciTech Connect

Composite cathode materials in lithium ion batteries have become the subject of a great amount of research recently as cost and safety issues related to LiCoO2 and other layered structures have been discovered. Alternatives to these layered materials include materials with the spinel and olivine structures, but these present different problems, e.g. spinels have low capacities and cycle poorly at elevated temperatures, and olivines exhibit extremely low intrinsic conductivity. Previous work has shown that composite structures containing spinel and layered materials have shown improved electrochemical properties. These types of composite structures have been studied in order to evaluate their performance and safety characteristics necessary for use in lithium ion batteries in portable electronic devices, particularly hybrid-electric vehicles. In this study, we extended that work to layered-olivine and spinel-olivine composites. These materials were synthesized from precursor salts using three methods: direct reaction, ball-milling, and a coreshell synthesis method. X-ray diffraction spectra and electrochemical cycling data show that the core-shell method was the most successful in forming the desired products. The electrochemical performance of the cells containing the composite cathodes varied dramatically, but the low overpotential and reasonable capacities of the spinel-olivine composites make them a promising class for the next generation of lithium ion battery cathodes.

Ward, R.M.; Vaughey, J.T.

2006-01-01

255

nature materials | VOL 7 | FEBRUARY 2008 | www.nature.com/naturematerials 105 REVIEW ARTICLE  

E-print Network

nature materials | VOL 7 | FEBRUARY 2008 | www.nature.com/naturematerials 105 REVIEW ARTICLE G. JEFFREY SNYDER* AND ERIC S. TOBERER Materials Science, California Institute of Technology, 1200 East throughnanostructuralengineering,whichledtoexperimentale orts to demonstrate the proof-of-principle and high-e ciency materials5

Wu, Zhigang

256

Examination of conversion degree of composite insulating materials  

Microsoft Academic Search

Composite insulating materials have their important place in high-voltage insulating technology. The quality and high reliability of electrical devices is much affected by the curing level of these materials. Curing level is quantified by so-called degree of conversion and there are several possibilities how to determine this degree in practice. Attention is given mainly to kinetic analysis based techniques. Kinetic

V. Mentlik; R. Polansky

2007-01-01

257

3D Magnetic Reluctivity Tensor of Soft Magnetic Composite Material  

Microsoft Academic Search

Soft magnetic composite (SMC) materials are particularly suitable for construction of electrical machines with complex structure and 3D magnetic flux. For design and analysis of such 3D flux machines, 3D magnetic properties of the magnetic materials should be properly determined, modeled and applied for calculating the magnetic field distribution, parameters and performance. This paper presents the 3D magnetic property measurement

Y. G. Guo; J. G. Zhu; Z. W. Lin; J. J. Zhong; H. Y. Lu; S. H. Wang

2006-01-01

258

SIMULATION OF DELAMINATION UNDER HIGH CYCLE FATIGUE IN COMPOSITE MATERIALS  

Microsoft Academic Search

Mechanical fatigue, especially high-cycle fatigue, is a common cause of failure of aerospace structures. In laminated composite materials, the fatigue process involves several damage mechanisms that result in the degradation of the material. One of the most important fatigue damage mechanisms is interlaminar damage (delamination), especially in the case of laminated structures devoid of reinforcement in the thickness direction. There

Albert Turon; Josep Costa; Pedro P. Camanho; Carlos G. Davila

259

Natural Cellulosic Substance Derived Nano-structured Materials  

Microsoft Academic Search

\\u000a When versatile synthetic chemical processes meet natural biological assemblies, a promising shortcut for the design and fabrication\\u000a of functional materials with tailored structures and properties are lit up. By precisely replicating natural substrates with\\u000a guest matrices, artificial materials are endowed with the initial biological structures and morphologies. To achieve faithful\\u000a inorganic\\/organic replicas of the natural species for the corresponding finest

Yuanqing Gu; Jianguo Huang

260

ADSORPTION OF ORGANIC CATIONS TO NATURAL MATERIALS  

EPA Science Inventory

The factors that control the extent of adsorption of amphiphilic organic cations on environmental and pristine surfaces have been studied. The sorbents were kaolinite, montmorillonite, two aquifer materials, and a soil; solutions contained various concentrations of NaCl and CaCl,...

261

ADSORPTION OF ORGANIC CATIONS TO NATURAL MATERIALS  

EPA Science Inventory

The factors that control the extent of adsorption of amphiphilic organic cations on environmental and pristine surfaces have been studied. he sorbents were kaolinite, montmorillonite, two aquifer materials, and a soil; solutions contained various concentrations of NaCl and CaC12,...

262

Polymeric compositions incorporating polyethylene glycol as a phase change material  

DOEpatents

A polymeric composition comprising a polymeric material and polyethylene glycol or end-capped polyethylene glycol as a phase change material, said polyethylene glycol and said end-capped polyethylene glycol having a molecular weight greater than about 400 and a heat of fusion greater than about 30 cal/g; the composition is useful in making molded and/or coated materials such as flooring, tiles, wall panels and the like; paints containing polyethylene glycols or end-capped polyethylene glycols are also disclosed.

Salyer, Ival O. (Dayton, OH); Griffen, Charles W. (Mason, OH)

1989-01-01

263

Isolation of Methylcobalamin from Natural Source Material  

Microsoft Academic Search

INVESTIGATION of the form of vitamin B12 in human blood plasma by chromatographic-bioautographic analysis revealed as the major component a `fourth factor' besides DMB coenzyme (coenzyme B12) and traces of hydroxo-cobalamin and cyanocobalamin1. This factor was also found in liver, E. coli and Streptomyces rimosus. In order to identify this analogue we have tried to isolate it from a natural

K. Lindstrand

1964-01-01

264

Composite material fabrication techniques. CRADA final report  

SciTech Connect

This report describes a low cost method of fabricating components for mockups and training simulators used in the transportation industry. This technology was developed jointly by the Oak Ridge National Laboratory (ORNL) and Metters Industries, Incorporated (MI) as part of a Cooperative Research and Development Agreement (CRADA) ORNL94-0288 sponsored by the Department of Energy (DOE) Office of Economic Impace and Diversity Minority Business Technology Transfer Consortium. The technology involves fabricating component replicas from fiberglass/epoxy composites using a resin transfer molding (RTM) process. The original components are used as masters to fabricate the molds. The molding process yields parts that duplicate the significant dimensional requirements of the original component while still parts that duplicate the significant dimensional requirements of the original component while still providing adequate strength and stiffness for use in training simulators. This technology permits MI to overcome an acute shortage in surplus military hardware available to them for use in manufacturing training simulators. In addition, the cost of the molded fiberglass components is expected to be less than that of procuring the original components from the military.

Frame, B J; Paulauskas, F L [Oak Ridge National Lab., TN (United States); Miller, J; Parzych, W [Metters Industries, Inc. (United States)

1996-09-30

265

Biotransformation of an uncured composite material  

NASA Technical Reports Server (NTRS)

The feasibility of biologically degrading prepreg wastes was studied. The work was conducted with the intention of obtaining baseline data that would facilitate the achievement of two long-range goals. These goals are: (1) the biological remediation of the hazardous components in the prepreg wastes, and (2) providing the potential for recycling the prepreg waste fibers. The experiments examined a prepreg that employs an bismaleimide resin system. Initial results demonstrated an obvious deterioration of the prepreg material when incubated with several bacterial strains. The most active cultures were identified as a mixture of 'Bacillus cereus' and 'Pseudomonas sp'. Gas chromatography analyses revealed seven primary compounds in the resin mixture. Biotransformation studies, using the complete prepreg material, demonstrated on obvious loss of all seven organic compounds. Gas chromatography-mass spectrometry analyses resulted in structure assignments for the two primary components of the resin. Both were analogs of Bisphenol A; one being bismaleimide, and the other being Bisphenol A containing a diglycidyl moiety. The 'diglycidyl analog' was purified using thin-layer chromatography and the biotransformation of this compound (at 27 ug/ml bacterial culture) was monitored. After a seven-day incubation, approximately 40% of the organic compound was biotransformed. These results demonstrate the biotransformation of the prepreg resin and indicate that biological remediation of the prepreg wastes is feasible.

Welsh, Clement J.; Glass, Michael J.; Cheslack, Brian; Pryor, Robert; Tran, Duan K.; Bowers-Irons, Gail

1994-01-01

266

Natural fibres as reinforcement in polylactic acid (PLA) composites  

Microsoft Academic Search

The focus in this work has been to study if natural fibres can be used as reinforcement in polymers based on renewable raw materials. The materials have been flax fibres and polylactic acid (PLA). PLA is a thermoplastic polymer made from lactic acid and has mainly been used for biodegradable products, such as plastic bags and planting cups, but in

K. Oksman; M. Skrifvars; J.-F. Selin

2003-01-01

267

A grammatical approach to customization of shape and composite materials  

NASA Astrophysics Data System (ADS)

With the increasing use of composite materials in Mechanical and Aerospace industries, an approach is required to facilitate designing of components using composite materials, while ensuring customization of the shape such a way that multiple design goals for the components are satisfied. Existing design methods may be used in some cases, where the component shape and loadings are simple. While a significant amount of research has been conducted to study the properties of composite materials, little attention has been paid to find out a design approach such that (1) the user requirements in the very general form may be used directly and as the input for the design, (2) the best possible composite material are selected to meet multiple desired functions, and (3) shape variation is analyzed in order to enable mass customization of the design. Thus an approach is required that will be able to handle both the shape and the material in order to design a load bearing component using composite materials. In this research the focus is to develop a design approach that will consider the user requirements for a composite component in its very general form and generate component shape and material details in a systematic order so that the designed component can withstand a given loading condition. Consequently, the Primary Research Question is: How to simultaneously explore shape and composite materials during the design of a product to meet multiple property and functional goals? The wide range of properties, covered by various fiber-matrix combinations, along with their directional property characteristics, maximizes the flexibility of the designers, while designing composite material products. Meeting multiple property goals, however, complicates the design process as both the composite material selection and the component shape formation becomes highly intricate with the loading conditions and a number of matrix calculations needs to be performed to determine theoretical value of composite material properties. A grammar is a formal definition of a language written in transformational form. To address these issues, in this research a grammatical approach is developed that will generate a shape grammar to perform shape optimization, and then incorporate a composite material selection system and loading analysis techniques of Solid Mechanics in order to design load bearing components of irregular shape. The approach will be able to consider the user requirements in the very general text form, convert them to the design requirements for the component, generate optimized shape based on multiple design constraints, perform the complete design work, and generate the component. The major contributions include: (1) generating a shape grammar to represent functions of the load bearing component such a way that mass-customization of shape is possible, (2) developing a composite material customization system in order to satisfy directional property requirements, and (3) introducing a unique laminate design approach in order to satisfy design property requirements at the critical cross-sections locally that can result in highly efficient design compared to conventional design method. Verification of the approach will focus on its application to simultaneously explore shapes and customization of composite materials.

Nandi, Soumitra

268

Quantitative measurement of nanomechanical properties in composite materials  

NASA Astrophysics Data System (ADS)

In this work, quantitative Atomic force acoustic microscopy (AFAM) was used to measure nanomechanical properties and to determine microstructural morphology in fiber reinforced composites and hard calcified tissue. In carbon fiber reinforced composites, the fiber-matrix interphase is of interest as it affects the primary load-transfer process and thereby bulk mechanical properties of reinforced composites. The study of properties in the interphase region is important for an understanding of the bulk mechanical properties, which have been shown affected by moisture-based environmental degradation. Single point AFAM testing has been used to quantitatively determine elastic properties at the fiber-matrix interphase by taking advantage of the high spatial scanning resolution capable of measuring interphase dimensions. Carbon-fiber epoxy composite samples were degraded in laboratory conditions by exposure to a accelerated hydrothermal degradation environment in deionized water and salt water. Composite degradation has been characterized by the change in the epoxy matrix contact stiffness and the interphase properties. A decrease in matrix stiffness was found to coincide with the environmental exposure and moisture absorption of the samples. Interphase stiffness measurements indicate a constant interphase thickness as a function of environmental exposure. Chemical analysis of the epoxy using FTIR and Raman spectroscopy indicate hydrolysis of the C-O-C and Epoxide bonds which contribute to the decrease in epoxy mechanical properties. Accelerated degradation by salt water and deionized water both resulted in degradation of the epoxy, though the presence of sodium chloride showed less degradation. From SEM, debonding of the fiber-matrix interface was observed to be more severe when exposed to a salt water environment. In performing quantitative AFAM measurements, the effects of tip shape on the contact mechanics at the epoxy interface were found to influence the reported results significantly, and new, power-law body of revolution models of the probe tip geometry have been applied. Due to the low yield strength of polymers compared with other engineering materials, elastic-plastic contact is considered to better represent the epoxy surface response and was used to acquire more accurate quantitative measurements. Visco-elastic contact response was introduced in the boundary condition of the AFAM cantilever vibration model, due to the creep nature of epoxy, to determine time-dependent effects. These methods have direct impact on the quantitative measurement capabilities of near-filler interphase regions in polymers and composites and the long-term influence of environmental conditions on composites. In addition, quantitative AFAM scans were made on distal surfaces of human bicuspids and molars, to determine the microstructural and spatial variation in nanomechanical properties of the enamel biocomposite. Single point AFAM measurements were performed on individual enamel prism and sheath locations to determine spatial elastic modulus. Mechanical property variation of enamel is associated to the differences in the mineral to organic content and the apatite crystal orientations within the enamel microstructure. Also, variation in the elastic modulus of the enamel ultrastructure was observed in measurements at the outer enamel versus near the dentine enamel junction (DEJ).

Zhao, Wei

269

The Yeh-Stratton Criterion for Composite Materials  

Microsoft Academic Search

A new criterion for composite failure is proposed based on the Yeh Stratton (Y-S) criterion which is proven to work well for isotropic materials. Since the Y-S criterion requires three yield strengths from simple tension, compression, and torsion tests, the Y-S criterion can be applicable for ductile materials as well as brittle materials with different strengths in tension and compression.

Hsien-Yang Yeh; Chang H. Kim

1994-01-01

270

Measurement of Damping of Composite Materials for Turbomachinery Applications  

NASA Technical Reports Server (NTRS)

The scientific community has felt that ceramic matrix composite (CMC) materials possess more material damping than the superalloys used in the production of rocket engine turbomachinery turbine-end components. The purpose of this NASA/MFSC study is to quantify the damping in CMC's as compared to a typical super-alloy, Inconel 718. It was observed through testing of beam coupons and disk specimens that the CMC's do indeed possess more material damping than the baselined alloy Inconel 718.

Harris, D. L.

1998-01-01

271

Statistical prediction of fatigue failure of fibre reinforced composite materials  

Microsoft Academic Search

A statistical approach is proposed to evaluate the residual strength and life of unidirectional and angle-ply composite laminates subjected to in-plane tensile cyclic stresses. The method is based on the extension of previous static failure criteria describing independently the fibre failure and matrix failure modes, combined with the statistical nature of fatigue failure of fibre-reinforced composites. The static and fatigue

Xiaoxue Diao; Lin Ye; Yiu-Wing Mai

1995-01-01

272

Fracture toughness of fibrous composite materials  

NASA Technical Reports Server (NTRS)

Laminates with various proportions of 0 deg, 45 deg, and 90 deg plies were fabricated from T300/5208 and T300/BP-907 graphite/epoxy prepreg tape material. The fracture toughness of each laminate orientation or lay-up was determined by testing center-cracked specimens, and it was also predicted with the general fracture-toughness parameter. The predictions were good except when crack-tip splitting was large, at which time the toughness and strengths tended to be underpredicted. By using predictions, a parametric study was also made of factors that influence fracture toughness. Fiber and matrix properties as well as lay-up were investigated. Without crack-tip splitting, fracture toughness increases in proportion to fiber strength and fiber volume fraction, increases linearly with E(22)/E(11), is largest when the modulus for non-0 deg fibers is greater than that of 0 deg fibers, and is smallest for 0(m)/90(p)(s) lay-ups. (The E(11) and E(22) are Young's moduli of the lamina parallel to and normal to the direction of the fibers, respectively). For a given proportion of 0 deg plies, the most notch-sensitive lay-ups are 0(m)/90(p)(s) and the least sensitive are 0(m)/45(n)(s) and alpha(s). Notch sensitivity increases with the proportion of 0 deg plies and decreases with alpha. Strong, tough matrix materials, which inhibit crack-tip splitting, generally lead to minimum fracture toughness.

Poe, C. C., Jr.

1984-01-01

273

Development of chemical vapor composites, CVC materials. Final report  

SciTech Connect

Industry has a critical need for high-temperature operable ceramic composites that are strong, non-brittle, light weight, and corrosion resistant. Improvements in energy efficiency, reduced emissions and increased productivity can be achieved in many industrial processes with ceramic composites if the reaction temperature and pressure are increased. Ceramic composites offer the potential to meet these material requirements in a variety of industrial applications. However, their use is often restricted by high cost. The Chemical Vapor composite, CVC, process can reduce the high costs and multiple fabrication steps presently required for ceramic fabrication. CVC deposition has the potential to eliminate many difficult processing problems and greatly increase fabrication rates for composites. With CVC, the manufacturing process can control the composites` density, microstructure and composition during growth. The CVC process: can grow or deposit material 100 times faster than conventional techniques; does not require an expensive woven preform to infiltrate; can use high modulus fibers that cannot be woven into a preform; can deposit composites to tolerances of less than 0.025 mm on one surface without further machining.

NONE

1998-10-05

274

Composite materials research and education program: The NASA-Virginia Tech composites program  

NASA Technical Reports Server (NTRS)

Major areas of study include: (1) edge effects in finite width laminated composites subjected to mechanical, thermal and hygroscopic loading with temperature dependent material properties and the influence of edge effects on the initiation of failure; (2) shear and compression testing of composite materials at room and elevated temperatures; (3) optical techniques for precise measurement of coefficients of thermal expansion of composites; (4) models for the nonlinear behavior of composites including material nonlinearity and damage accumulation and verification of the models under biaxial loading; (5) compressive failure of graphite/epoxy plates with circular holes and the buckling of composite cylinders under combined compression and torsion; (6) nonlinear mechanical properties of borsic/aluminum, graphite/polyimide and boron/aluminum; (7) the strength characteristics of spliced sandwich panels; and (8) curved graphite/epoxy panels subjected to internal pressure.

Herakovich, C. T.

1980-01-01

275

Probabilistic fatigue life prediction of metallic and composite materials  

NASA Astrophysics Data System (ADS)

Fatigue is one of the most common failure modes for engineering structures, such as aircrafts, rotorcrafts and aviation transports. Both metallic materials and composite materials are widely used and affected by fatigue damage. Huge uncertainties arise from material properties, measurement noise, imperfect models, future anticipated loads and environmental conditions. These uncertainties are critical issues for accurate remaining useful life (RUL) prediction for engineering structures in service. Probabilistic fatigue prognosis considering various uncertainties is of great importance for structural safety. The objective of this study is to develop probabilistic fatigue life prediction models for metallic materials and composite materials. A fatigue model based on crack growth analysis and equivalent initial flaw size concept is proposed for metallic materials. Following this, the developed model is extended to include structural geometry effects (notch effect), environmental effects (corroded specimens) and manufacturing effects (shot peening effects). Due to the inhomogeneity and anisotropy, the fatigue model suitable for metallic materials cannot be directly applied to composite materials. A composite fatigue model life prediction is proposed based on a mixed-mode delamination growth model and a stiffness degradation law. After the development of deterministic fatigue models of metallic and composite materials, a general probabilistic life prediction methodology is developed. The proposed methodology combines an efficient Inverse First-Order Reliability Method (IFORM) for the uncertainty propogation in fatigue life prediction. An equivalent stresstransformation has been developed to enhance the computational efficiency under realistic random amplitude loading. A systematical reliability-based maintenance optimization framework is proposed for fatigue risk management and mitigation of engineering structures.

Xiang, Yibing

276

Holographic imaging of natural-fiber-containing materials  

DOEpatents

The present invention includes methods and apparatuses for imaging material properties in natural-fiber-containing materials. In particular, the images can provide quantified measures of localized moisture content. Embodiments of the invention utilize an array of antennas and at least one transceiver to collect amplitude and phase data from radiation interacting with the natural-fiber-containing materials. The antennas and the transceivers are configured to transmit and receive electromagnetic radiation at one or more frequencies, which are between 50 MHz and 1 THz. A conveyance system passes the natural-fiber-containing materials through a field of view of the array of antennas. A computing device is configured to apply a synthetic imaging algorithm to construct a three-dimensional image of the natural-fiber-containing materials that provides a quantified measure of localized moisture content. The image and the quantified measure are both based on the amplitude data, the phase data, or both.

Bunch, Kyle J [Richland, WA; Tucker, Brian J [Pasco, WA; Severtsen, Ronald H [Richland, WA; Hall, Thomas E [Kennewick, WA; McMakin, Douglas L [Richland, WA; Lechelt, Wayne M [West Richland, WA; Griffin, Jeffrey W [Kennewick, WA; Sheen, David M [Richland, WA

2010-12-21

277

The role of polymer based composites materials in modern and future aerospace structures  

NASA Astrophysics Data System (ADS)

The need to reduce the overall weight of aeronautical and space structures, while at the same time preserving or even improving their performances, make the research and development in the field of innovative structures and advanced composite materials a crucial step for the advancement of aerospace technologies. Several fields of innovation have been explored in the last decades but the most promising solutions for the future of aerospace structures will be found in the "intelligent" use of polymer based composite materials both in the design and in their "nature like" use.

Cantoni, Stefania; De Nicola, Felice; Mercurio, Umberto; Quaranta, Vincenzo

2014-05-01

278

Functional hybrid materials derived from natural cellulose  

NASA Astrophysics Data System (ADS)

In this paper, we report a study on the optical and the electrical properties of pure cotton fibers (CF) from chemically surface- and morphology-modified samples coated with poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) polymer by using a dip-coating method. The properties of the treated and coated fibers were characterized by using scanning electron microscopy (SEM), luminescence and I- V characteristics. The performance of fibers with MEH-PPV polymer as a coating component was investigated, and an excellent white-light emission that consisted of blue-, green-, and red-light-emitting bands was demonstrated. The I- V characteristics of sandwich-type devices consisting of successive layers of ITO (Indium doped tin oxide coated glass)-PEDOT-PSS (Poly(3,4-ethylenedioxythiophene)-Poly(styrenesulfonate)-CF/MEH-PPV-Ag showed that upon light illumination, the current increased in both the forward and the reverse bias conditions which suggest that the photoresponse parameters for the heterojunction are better than they are for the composite alone.

Zakirov, A. S.; Yuldashev, Sh. U.; Cho, H. D.; Lee, J. C.; Kang, T. W.; Khamdamov, J. J.; Mamadalimov, A. T.

2012-05-01

279

Life Modeling and Design Analysis for Ceramic Matrix Composite Materials  

NASA Technical Reports Server (NTRS)

The primary research efforts focused on characterizing and modeling static failure, environmental durability, and creep-rupture behavior of two classes of ceramic matrix composites (CMC), silicon carbide fibers in a silicon carbide matrix (SiC/SiC) and carbon fibers in a silicon carbide matrix (C/SiC). An engineering life prediction model (Probabilistic Residual Strength model) has been developed specifically for CMCs. The model uses residual strength as the damage metric for evaluating remaining life and is posed probabilistically in order to account for the stochastic nature of the material s response. In support of the modeling effort, extensive testing of C/SiC in partial pressures of oxygen has been performed. This includes creep testing, tensile testing, half life and residual tensile strength testing. C/SiC is proposed for airframe and propulsion applications in advanced reusable launch vehicles. Figures 1 and 2 illustrate the models predictive capabilities as well as the manner in which experimental tests are being selected in such a manner as to ensure sufficient data is available to aid in model validation.

2005-01-01

280

Simulation of composite material response under dynamic compressive loading  

SciTech Connect

Realistic computer prediction of high-velocity impact and penetration events involving composite materials requires a knowledge of the material behavior under large compressive stresses at high rates of deformation. As an aid to the development of constitutive models for composites under these conditions, methods for numerical simulation of the material response at the microstructural level are being developed. At present, the study is confined to glass fiber/epoxy composites. The technique uses a numerical model of a representative sample of the microstructure with randomly distributed fibers. By subjecting the boundary of this numerical sample to prescribed loading histories, a statistical interpretation allows prediction of the global material response. Because the events at the microstructural scale involve locally large deformation, and because of the constantly changing picture with regard to contact between the fibers, the Eulerian code CTH is used for these calculations. Certain aspects of material failure can also be investigated using this approach. The method allows the mechanical behavior of composite materials to be studied with fewer assumptions about constituent behavior and morphology than typically required in analytical efforts.

Silling, S.A.; Taylor, P.A.

1993-12-31

281

Experimental Investigation of Textile Composite Materials Using Moire Interferometry  

NASA Technical Reports Server (NTRS)

The viability as an efficient aircraft material of advanced textile composites is currently being addressed in the NASA Advanced Composites Technology (ACT) Program. One of the expected milestones of the program is to develop standard test methods for these complex material systems. Current test methods for laminated composites may not be optimum for textile composites, since the architecture of the textile induces nonuniform deformation characteristics on the scale of the smallest repeating unit of the architecture. The smallest repeating unit, also called the unit cell, is often larger than the strain gages used for testing of tape composites. As a result, extending laminated composite test practices to textiles can often lead to pronounced scatter in material property measurements. It has been speculated that the fiber architectures produce significant surface strain nonuniformities, however, the magnitudes were not well understood. Moire interferometry, characterized by full-field information, high displacement sensitivity, and high spatial resolution, is well suited to document the surface strain on textile composites. Studies at the NASA Langley Research Center on a variety of textile architectures including 2-D braids and 3-D weaves, has evidenced the merits of using moire interferometry to guide in test method development for textile composites. Moire was used to support tensile testing by validating instrumentation practices and documenting damage mechanisms. It was used to validate shear test methods by mapping the full-field deformation of shear specimens. Moire was used to validate open hole tension experiments to determine the strain concentration and compare then to numeric predictions. It was used for through-the-thickness tensile strength test method development, to verify capabilities for testing of both 2-D and 3-D material systems. For all of these examples, moire interferometry provided vision so that test methods could be developed with less speculation and more documentation.

Ifju, Peter G.

1995-01-01

282

Pin bearing evaluation of LTM25 composite materials  

NASA Technical Reports Server (NTRS)

This report summarizes pin bearing evaluations of LTM25 composite materials. Northrop Grumman Corporation conducted pin bearing testing and fabricate two panels from composite materials that cure at low temperatures. These materials are being incorporated into Unmanned Aerial Vehicles (UAVS) to reduce manufacturing costs since they allow the use of low-cost tooling and facilities. Two composite prepreg product forms were evaluated; MR50/LTM25 unidirectional tape, batch 2881vd and CFS003/LTM25 woven cloth, batch 2216. Northrop Grumman fabricated, machined, and tested specimens to determine the bearing strength in accordance with MIL-HDBK-17D, Volume 1, Section 7.2.4. Quasi-isotropic laminates from the two product forms were fabricated for these tests. In addition, 2 quasi-isotropic panels of dimensions 12 in. x 28 in. were fabricated (one each from the two product forms), inspected, and shipped to NASA Langley for further evaluation.

Shah, C. H.; Postyn, A. S.

1996-01-01

283

Brazing of sheet composite materials with aluminium matrix  

NASA Astrophysics Data System (ADS)

The technique of brazing composite sheets with an aluminum matrix is investigated for Al matrices with either stainless steel or boron fibers. Brazing is compared to other joining techniques, and the relationship between heating and pressure levels is studied by characterizing the joint qualities microscopically. Solder composition is similarly analyzed, and brazing recommendations are given for ranges of joint sizes. Calculations of the temperature fields for the brazing of these composite materials yield specific-heat input data. Optimal brazing modes thus derived for the Al-matrix composites yield joints free of the intermetallide phases that degrade the performance of brazed structures. The tensile strength of the optimized joints is shown to be good relative to the strength of the original composites with Al matrices.

Khorunov, V. F.; Kuchuk-Iatsenko, V. S.; Dykhno, I. S.; Kasatkina, N. V.

284

Delamination, durability and damage tolerance of laminated composite materials  

NASA Technical Reports Server (NTRS)

Research exploring the role of delamination on the durability and damage tolerance of advanced composite materials is reviewed. Recent studies on the characterization of composite delamination are summarized. Recent analytical solutions for interlaminar stresses and strain energy release rates associated with common sources of delamination are also reviewed. The role of delamination in low velocity impact, residual compression strength, and in fatigue is highlighted. Delamination is shown to be the common damage mode observed in all of these problems. A Damage Threshold/Fail-safety concept for addressing composite damage tolerance is discussed.

O'Brien, T. K.

1991-01-01

285

Flame-Resistant Composite Materials For Structural Members  

NASA Technical Reports Server (NTRS)

Matrix-fiber composite materials developed for structural members occasionally exposed to hot, corrosive gases. Integral ceramic fabric surface layer essential for resistance to flames and chemicals. Endures high temperature, impedes flame from penetrating to interior, inhibits diffusion of oxygen to interior where it degrades matrix resin, resists attack by chemicals, helps resist erosion, and provides additional strength. In original intended application, composite members replace steel structural members of rocket-launching structures that deteriorate under combined influences of atmosphere, spilled propellants, and rocket exhaust. Composites also attractive for other applications in which corrosion- and fire-resistant structural members needed.

Spears, Richard K.

1995-01-01

286

Interdisciplinary research concerning the nature and properties of ceramic materials  

NASA Technical Reports Server (NTRS)

The nature and properties of ceramic materials as they relate to solid state physics and metallurgy are studied. Special attention was given to the applications of ceramics to NASA programs and national needs.

1975-01-01

287

Multi-objective shape and material optimization of composite structures including damping  

NASA Technical Reports Server (NTRS)

A multi-objective optimal design methodology is developed for light-weight, low cost composite structures of improved dynamic performance. The design objectives include minimization of resonance amplitudes (or maximization of modal damping), weight, and material cost. The design vector includes micromechanics, laminate, and structural shape parameters. Performance constraints are imposed on static displacements, dynamic amplitudes, and natural frequencies. The effects of damping on the dynamics of composite structures are incorporated. Preliminary applications on a cantilever composite beam illustrated that only the proposed multi-objective optimization, as opposed to single objective functions, simultaneously improved all objectives. The significance of composite damping in the design of advanced composite structures was also demonstrated, indicating the design methods based on undamped dynamics may fail to improve the dynamic performance near resonances.

Saravanos, D. A.; Chamis, Christos C.

1990-01-01

288

Development of biomimetical composite prosthetic ligaments using mechanically dissimilar materials  

Microsoft Academic Search

Using high performance textile materials and novel designs, structures were developed which have the potential for mimicking the properties of natural anterior cruciate ligaments (ACLs). Six tubular braided structures capable of withstanding the loads encountered by ACL, were built. Elastomeric materials were incorporated as cores in order to give the devices the ability to recover from strains. Mechanical and viscoelastic

F. T. Moutos; B. S. Gupta

1999-01-01

289

Novel Composite Materials for SOFC Cathode-Interconnect Contact  

SciTech Connect

This report summarized the research efforts and major conclusions of our University Coal Research Project, which focused on developing a new class of electrically-conductive, Cr-blocking, damage-tolerant Ag-perovksite composite materials for the cathode-interconnect contact of intermediate-temperature solid oxide fuel cell (SOFC) stacks. The Ag evaporation rate increased linearly with air flow rate initially and became constant for the air flow rate {ge} {approx} 1.0 cm {center_dot} s{sup -1}. An activation energy of 280 KJ.mol{sup -1} was obtained for Ag evaporation in both air and Ar+5%H{sub 2}+3%H{sub 2}O. The exposure environment had no measurable influence on the Ag evaporation rate as well as its dependence on the gas flow rate, while different surface morphological features were developed after thermal exposure in the oxidizing and reducing environments. Pure Ag is too volatile at the SOFC operating temperature and its evaporation rate needs to be reduced to facilitate its application as the cathode-interconnect contact. Based on extensive evaporation testing, it was found that none of the alloying additions reduced the evaporation rate of Ag over the long-term exposure, except the noble metals Au, Pt, and Pd; however, these noble elements are too expensive to justify their practical use in contact materials. Furthermore, the addition of La{sub 0.8}Sr{sub 0.2}MnO{sub 3} (LSM) into Ag to form a composite material also did not significantly modify the Ag evaporation rate. The Ag-perovskite composites with the perovskite being either (La{sub 0.6}Sr{sub 0.4})(Co{sub 0.8}Fe{sub 0.2})O{sub 3} (LSCF) or LSM were systematically evaluated as the contact material between the ferritic interconnect alloy Crofer 22 APU and the LSM cathode. The area specific resistances (ASRs) of the test specimens were shown to be highly dependent on the volume percentage and the type of the perovskite present in the composite contact material as well as the amount of thermal cycling that the specimens were subjected to during testing. The Ag-LSCF composite contact materials proved more effective in trapping Cr within the contact material and preventing Cr migration into the cathode than the Ag-LSM composites. Ag-perovskite composite contact materials are promising candidates for use in intermediate-temperature SOFC stacks with ferritic stainless steel interconnects due to their ability to maintain acceptably low ASRs while reducing Cr migration into the cathode material.

J. H. Zhu

2009-07-31

290

382 NATURE MATERIALS | VOL 12 | MAY 2013 | www.nature.com/naturematerials news & views  

E-print Network

they want. The institute houses, among other things, a state-of- the-art laser cutter, a 3D printer382 NATURE MATERIALS | VOL 12 | MAY 2013 | www.nature.com/naturematerials news & views C ollective excitations such as phonons, the atomic or molecular vibrations that transport heat in a material, have always

McGaughey, Alan

291

478 NATURE MATERIALS | VOL 12 | JUNE 2013 | www.nature.com/naturematerials news & views  

E-print Network

, of three-dimensional (3D) tissue-like materials that fold in ways similar to muscles and, like neural tissues, transmit electrical signals3 (Fig. 1). Bayley and co-workers used an automated 3D printer478 NATURE MATERIALS | VOL 12 | JUNE 2013 | www.nature.com/naturematerials news & views T o make

Demirci, Utkan

292

100 NATURE MATERIALS | VOL 12 | FEBRUARY 2013 | www.nature.com/naturematerials news & views  

E-print Network

. Rev. Lett. 109, 257203; 2012). The researchers examine frustration arising in certain geometric minimal-energy state even at absolute zero. By analogy, some magnetic materials with a lattice of corner100 NATURE MATERIALS | VOL 12 | FEBRUARY 2013 | www.nature.com/naturematerials news & views

Mahadevan, L.

293

Natural Radioactivity of Quarry raw Material in Israel  

NASA Astrophysics Data System (ADS)

During the past decade Natural Occurring Radioactive Material (NORM) has been receiving growing attention by radiation protection agencies, including chronic exposure to radon and radiation from building materials. A new Israeli standard (5098) which limit the radionuclide concentration in building material entered into force in 2003. Building materials are often made of natural raw materials which contain natural radionuclides from the 238U-226Ra, 232Th decay series and 40K that occur naturally in the Earth's crust. The radionuclide concentration in the building material depends on the source of the raw material, manufacturing process and the addition of technically enhanced NORM (Te NORM) like fly ash, phospho-gypsum, etc. The aim of this study was to investigate the spatial variation of the natural radioactivity in quarries in Israel, the dependency on the type of quarried substance and to asses the raw materials by radiation protection criteria. The study covered a total of 25 quarries all over Israel that manufacture different types of quarried substances (Limestone, Dolomite, Basalt, Gypsum etc.). Each of the quarries was sampled for three different aggregate sizes. The quarries were selected according to geological-geographical criteria such that all types of quarried materials throughout Israel will be investigated. The radionuclide measurement was performed by Gamma spectrometry according to standard procedures. A simulation was carried out on different concrete mixtures to asses the individual effective dose from the building materials. Results indicate large variations in the radionuclide concentration of raw materials in Israel. An optimization based on radiation protection criteria is proposed to minimize radiation exposure from building material.

Haquin, G.; Gazit-Yaari, N.; Yungreis, Z.; Braun, M.; Margaliot, M.

2004-12-01

294

Theories and Conflict: The Origins of Natural Gas. Instructional Materials.  

ERIC Educational Resources Information Center

This unit explores a recent and controversial theory of the origin of much of the Earth's natural gas and oil. The materials provided will give students the opportunity to: (1) gain an understanding of science and what is involved in the acceptance or rejection of theories; (2) learn about fossil fuels, especially natural gas; (3) learn the…

Anderson, Susan

295

Application of magnetic abrasive polishing to composite materials  

Microsoft Academic Search

Magnetic abrasive polishing (MAP) is an advanced machining process that can produce smoother surfaces in many material types.\\u000a The present study conducted an experimental assessment of MAP for a newly developed, non-ferrous and aluminum-based composite\\u000a material. A permanent magnet was installed under the workpiece to enhance its magnetic flux density, which had proved insufficient\\u000a for effective MAP. The success of

Tae-Wan Kim; Dae-Min Kang; Jae-Seob Kwak

2010-01-01

296

Inhibition of catalytic oxidation of carbon\\/carbon composite materials  

Microsoft Academic Search

An investigation coupling experimental efforts with computational chemistry analysis was conducted to study the inhibition effects of phosphorous or boron on the oxidation of carbon\\/carbon composite materials catalyzed by potassium or calcium acetate (KAC or CaAC). Commercial aircraft brakes were used, which are exposed during use to K- or Ca-containing runway deicing agents. The reactivity of inhibitor-doped carbon materials was

Xianxian Wu

2002-01-01

297

Raman spectroscopic analysis of Mexican natural artists’ materials  

Microsoft Academic Search

This work represents the Raman spectra of 15 natural artists’ materials that were obtained from local market in Mexico. Some of these products are not endemic to the region, but are often used in local conservation practice. Other materials are of local origin and have been used for centuries by local craftsmen. The Raman spectra that are reported here are:

Peter Vandenabeele; Mayahuel Ortega-Avilès; Dolores Tenorio Castilleros; Luc Moens

2007-01-01

298

Ultrasonic technique for extracting nanofibers from nature materials  

Microsoft Academic Search

This letter reports a simple and versatile approach for extracting bionanofibers from natural materials using the ultrasonic technique. Bionanofibers have been fabricated from various materials, e.g., spider and silkworm silks, chitin fibers, collagen, cotton, bamboo, and ramee and hemp fibers. The obtained nanofibers have uniform diameters in the range of 25-120 nm and possess the optimized hierarchical structures and superior

Hong-Ping Zhao; Xi-Qiao Feng; Huajian Gao

2007-01-01

299

2006 Nature Publishing Group Multiferroic and magnetoelectric materials  

E-print Network

© 2006 Nature Publishing Group Multiferroic and magnetoelectric materials W. Eerenstein1 , N. D few `multiferroic' materials that exhibit both of these properties, but the `magnetoelectric' coupling and typically involves terms such as `multiferroic' and `magnetoelectric', whose overlap is incomplete (Fig. 1

Chandra, Premi

300

Ptah-socar fuel-cooled composite materials structure  

NASA Astrophysics Data System (ADS)

One of the key points for the development of dual-mode ramjets operating up to Mach 8 or more is the mastery of fuel-cooled composite materials structures, which are needed, at least, for the combustion chamber. MBDA France and EADS ST have been working on the development of a particular technology for such structures taking advantage of the background of MBDA France in the field of dual-mode ramjet and fuel-cooled structures and of ASTRIUM-EADS ST in the field of high-temperature composite materials. They have developed an innovative technology for advanced monobloc cooled C/C/SiC structures. The paper gives an updated status of the development of Paroi Tissée Application Hypersonique - Simple Operational Composite for Advanced Ramjet (PTAH-SOCAR) technology, including test results, and presents some results obtained during system and demonstrator studies.

Bouchez, M.; Beyer, S.

2009-09-01

301

Dynamically Driven Phase Transformations in Damaged Composite Materials  

SciTech Connect

A model developed for composite materials undergoing dynamicaly driven phase transitions in its constituents has been extended to allow for complex material micro-structure and evolution of damage. In this work, damage is described by interfacial debonding and micro-crack growth. We have applied the analysis to silicon carbide-titanium (SiC-Ti) unidirectional metal matrix composites. In these composites, Ti can undergo a low pressure and temperature solid-solid phase transition. With these extensions we have carried out simulations to study the complex interplay between loading rates, micro-structure, damage, and the thermo-mechanical response of the system as it undergoes a solid-solid phase transitions.

Plohr, JeeYeon N. [Theoretical Division, MS B221, LANL, Los Alamos, NM 87545 (United States); Clements, Brad E.; Addessio, Frank L

2006-07-28

302

Efficient analysis of complex natural materials using LA-ICP-MS  

NASA Astrophysics Data System (ADS)

Many natural materials exhibit complex variations in chemical or isotopic composition over relatively short length scales, and these compositional variations often record important information about the environment or nature of the processes that lead to formation. Examples include complexly zoned crystals within volcanic rocks that record magmatic and volcanic signals, otoliths and other biominerals that record life history and environmental information, and speleothems that record climatic variables. Laser ablation ICP-MS analyses offer several advantages for quantifying compositional in chemically complex natural materials. These include the speed of analysis, the ability to sample at atmospheric pressures, the wide diversity of possible analytes, and the ability to make measurements in both spot and raster modes. The latter in particular offers advantages for analyses that require efficient acquisition of information over significant length scales, as in raster mode compositional data can be rapidly obtained by translating the laser laterally over a compositional variable material during a single analysis. In this fashion elemental or isotopic composition at a given analysis time corresponds to the lateral spatial dimension. This contrasts with a record obtained by a row of individual spots, which require a large number of discrete analyses, and requires significantly more analysis time. However there are also disadvantages to this style of analysis. Translation of the circular spots typically used for analysis results in significant signal attenuation and production of artifacts that may mirror natural diffusion profiles or other gradual changes. The ability to ablate using non-circular spots significantly reduces this effect, although the degree of attenuation is also increased by slower ablation cell response times. For single volume cells this may result in 50-100% additional attenuation than that produced by the translation of the spot alone, although two-volume and other rapid response cells significantly reduce this effect. Raster analyses are also highly sensitive to the presence of small contaminant phases along the raster trajectory, as the compositional signal from these can become attenuated and difficult to distinguish from natural compositional variations. It can also be difficult to establish exactly where compositional changes occur in materials that are visually homogenous. In this contribution we discuss these issues in more detail and present data acquisition and processing strategies that minimize these difficulties.

Kent, A. J.; Loewen, M. W.; Koleszar, A. M.; Miller, J.; Ungerer, C. "

2011-12-01

303

INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS 1. General Introduction  

E-print Network

Framework Directive [5] and the Directive on End Of Life Vehicles [6], thermoplastic CFRP (TP to a patent[9] clearly describing how strip pieces (chips) made of chopped thermoplastic pre FOR THE AEROSPACE WITH DISCONTINUOUS NOVELAND RECYCLED THERMOPLASTIC COMPOSITE MATERIALS N.Eguémann1, 2* , L.Giger1

Boyer, Edmond

304

NASA Composite Materials Development: Lessons Learned and Future Challenges  

NASA Technical Reports Server (NTRS)

Composite materials have emerged as the materials of choice for increasing the performance and reducing the weight and cost of military, general aviation, and transport aircraft and space launch vehicles. Major advancements have been made in the ability to design, fabricate, and analyze large complex aerospace structures. The recent efforts by Boeing and Airbus to incorporate composite into primary load carrying structures of large commercial transports and to certify the airworthiness of these structures is evidence of the significant advancements made in understanding and use of these materials in real world aircraft. NASA has been engaged in research on composites since the late 1960 s and has worked to address many development issues with these materials in an effort to ensure safety, improve performance, and improve affordability of air travel for the public good. This research has ranged from synthesis of advanced resin chemistries to development of mathematical analyses tools to reliably predict the response of built-up structures under combined load conditions. The lessons learned from this research are highlighted with specific examples to illustrate the problems encountered and solutions to these problems. Examples include specific technologies related to environmental effects, processing science, fabrication technologies, nondestructive inspection, damage tolerance, micromechanics, structural mechanics, and residual life prediction. The current state of the technology is reviewed and key issues requiring additional research identified. Also, grand challenges to be solved for expanded use of composites in aero structures are identified.

Tenney, Darrel R.; Davis, John G., Jr.; Pipes, R. Byron; Johnston, Norman

2009-01-01

305

Numerical Simulation of Delamination Growth in Composite Materials  

Microsoft Academic Search

Abstract The use of decohesion elements for the simulation of delamination in composite materials is reviewed The test methods available to measure the interfacial fracture toughness used in the formulation of decohesion elements are described initially After a brief presentation of the virtual crack closure technique, the technique most widely used to simulate delamination growth, the formulation of interfacial decohesion

P. P. Camanho; D. R. Ambur

2001-01-01

306

Development of active and sensitive material systems based on composites  

Microsoft Academic Search

This paper describes new concepts proposed by the author to realize active and sensitive structural material systems. Two examples of multifunctional composites were fabricated and evaluated in this study as follows: (1) An active laminate of aluminum plate (works as muscle), epoxy film (as insulator), unidirectional CFRP prepreg (as bone and blood vessel) and copper foil electrode (to apply voltage

Hiroshi Asanuma

2002-01-01

307

Inspection for kissing bonds in composite materials using vibration measurements  

NASA Astrophysics Data System (ADS)

Improper bonding of composite structures can result in close contact cracks under compressive stresses, called kissing bonds. These bond defects are very difficult to detect using conventional inspection techniques such as tap testing or local ultrasonic scanning and can lead to local propagation of damage if the structure is subjected to crack opening stresses. A method is investigated for identifying kissing bonds in composite material repairs based on vibration measurements. A damage feature of the kissing bond is extracted from the response of the input-output measurement that is a function of the structural path. This path exhibits local decoupling associated with the close contact cracks. Experimental vibration measurements from sandwich composite materials are presented along with the results of the damage detection algorithm for the healthy sections of the material and the kissing bond sections. A vibration based inspection technique could increase the ability to detect kissing bonds in composite material repairs while decreasing inspection time. Benefits of this method of identification over conventional techniques include its robust, objective damage detection methodology and the reduced requirement for specimen preparation and surface texture when compared to ultrasonic scanning.

Adams, Douglas E.; Sharp, Nathan D.; Myrent, Noah; Sterkenburg, Ronald

2011-04-01

308

Characterization of a High Strain Composite Material I. Maqueda  

E-print Network

respectively from the Weibull distribution of the strength of a single fiber combined with a simple bundle no damage, as elastic microbuckling of the fibers acts as a stress relief mechanism that prevents them from and developed a high-strain composite material consisting of car- bon fibers embedded in a silicone matrix

Pellegrino, Sergio

309

Design And Formability Of A New Composite Material  

SciTech Connect

Composite materials with metallic cover sheets have been established based on their low weight potential in industrial applications. Further requirements such as high stiffness of component, vibration damping and formability today are only partially met by these composites. For that reason, in current research work, great efforts are being made to develop materials which can be adapted to their later use and load in terms of improving noise, vibration and harshness. Thus, greater stiffness of component structure with a simultaneous reduction of weight can be achieved. This article presents a new composite material which consists of a plane sheet, a thin intermediate damping-layer and a sheet with formed elements to increase stiffness of component such as beads. The plane side can be used as the visible part side. The shape elements increase strength due to work hardening and can be used as design or functional elements. Thus, this composite material results in several advantages within the single layers. Possible flexibility in component design enables new semi-finished or tailored components.

Bolay, C.; Liewald, M. [Institute for Metal Forming Technology (IFU)-Holzgartenstr. 17, 70174 Stuttgart (Germany)

2011-05-04

310

Thermal Expansion Coefficients of Composite Materials Based on Energy Principles  

Microsoft Academic Search

Bounds on effective thermal expansion coefficients of isotropic and anisotropic composite materials consisting of isotropic phases are derived by employing extremum principles of thermoelasticity. Inequalities between certain approximate and exact forms of the potential and complementary energy functionals are first estab lished. These inequalities are then used in conjunction with a new method for minimizing the difference between upper and

R. A. Schapery

1968-01-01

311

Review of probabilistic models of the strength of composite materials  

Microsoft Academic Search

The available literature concerning probabilistic models describing the strength of composite materials has been reviewed to highlight the important aspects of this behaviour which will be of interest to the modelling and analysis of a complex system. The success with which these theories have been used to predict experimental results has been discussed. Since the brittle reinforcement phase largely controls

L. S. Sutherland; C. Guedes Soares

1997-01-01

312

Recycling By Solvolysis Thermosetting Composite Materials Of Sustainable Surface Transport  

Microsoft Academic Search

A solvolysis process is studied to degrade an unsaturated polyester resin based on DCPD (dicyclopentadiene) and crosslinked with styrene, as the matrix of a composite material reinforced with long glass fibers. The study presented here investigates in particular the hydrolysis in conditions below the critical point of water (T<374° C and P<221bar) in a batch reactor. Process window and parameter

Géraldine Oliveux; Eric Le Gal La Salle; Jean-Luc Bailleul

2011-01-01

313

Fractography of modern engineering materials: Composites and metals, Second volume  

SciTech Connect

This book contains the manuscripts of eleven papers that were presented at the Second Symposium on Fractography of Modern Engineering Materials held in May 1992. The numerous advances in materials science in the six year period following the First Symposium dictated this second meeting. Not only had new materials been developed in the intervening years, but understanding of older materials had also progressed. Similarly, advances in the technology and the techniques of fractography had occurred. The objective of the symposium was to extend the colloquy on fractography to include these many advances. The paper may be divided into three sections: Unique Fractographic Techniques; Metallic Materials; Polymeric and Composite Materials. The section titles reflect the diversity of materials discussed in the meeting. The range of materials included cross-linked polyethylene, AISI 52100 steel, 2024 aluminum, and a variety of organic and metal matrix fibrous composites. The case studies presented also covered a wide range. They included failure investigations of an antenna used in deep space exploration and chemical storage tanks. Advances in the techniques of fractography were also reflected in a number of presentations; quantitative techniques and expert systems were also subjects of presentations. A short precis of each paper is included here to assist the readers in identifying works of particular interest.

Masters, J.E.; Gilbertson, L.N. (eds.)

1993-01-01

314

Surface composites: A new class of engineered materials Rajiv Singh and James Fitz-Gerald  

E-print Network

are different from existing engineered materials such as "bulk composites" and "functionally graded materials, such that the phase composition is linearly graded as a function of distance from the surface. Surface composites composites and func- tionally graded materials (FGM) have been developed to combine desirable materials

Fitz-Gerald, James M.

315

Effect of natural organic materials on cadmium and neptunium sorption  

Microsoft Academic Search

In a batch sorption study of the effect of naturally occurring organic materials on the sorption of cadmium and neptunium on oxides and tuff surfaces, the model sorbents were synthetic goethite, boehmite, amorphous silicon oxides, and a crushed tuff material from Yucca Mountain, Nevada. An amino acid, 3-(3,4-dihydroxypheny)-DL-alanine (DOPA), and an aquatic-originated fulvic material, Nordic aquatic fulvic acid (NAFA), were

K. S. Kung; I. R. Triay

1994-01-01

316

Bamboo fibre filled natural rubber composites: the effects of filler loading and bonding agent  

Microsoft Academic Search

Bamboo fibre reinforced natural rubber composites were prepared by incorporation of different loadings of bamboo fibre. Two series of composites were studied i.e. composites with and without the presence of a bonding agent. The curing characteristics of the composites were determined and the composites were vulcanized at 150°C using a hot press. The properties of the composites such as tensile

Hanafi Ismail; M. R. Edyham; B. Wirjosentono

2002-01-01

317

Ultrasonic technique for extracting nanofibers from nature materials  

NASA Astrophysics Data System (ADS)

This letter reports a simple and versatile approach for extracting bionanofibers from natural materials using the ultrasonic technique. Bionanofibers have been fabricated from various materials, e.g., spider and silkworm silks, chitin fibers, collagen, cotton, bamboo, and ramee and hemp fibers. The obtained nanofibers have uniform diameters in the range of 25-120nm and possess the optimized hierarchical structures and superior properties of natural materials which have formed after the evolution of many millions of years. This methodology might be valuable to provide a convenient, versatile, and environmentally benign fabrication method for producing bionanofibers at an industrial scale.

Zhao, Hong-Ping; Feng, Xi-Qiao; Gao, Huajian

2007-02-01

318

Natural Lignocellulosic Fibers as Engineering Materials—An Overview  

NASA Astrophysics Data System (ADS)

Recent investigations on the tensile properties of natural cellulose-based fibers revealed an increasing potential as engineering materials. This is particularly the case of very thin fibers of some species such as sisal, ramie, and curaua. However, several other commonly used fibers such as flax, jute, hemp, coir, cotton, and bamboo as well as less known bagasse, piassava, sponge gourde, and buriti display tensile properties that could qualify them as engineering materials. An overview of the strength limits attained by these fibers is presented. Based on a tensile strength vs density chart, it is shown that natural fibers stand out as a relevant class of engineering materials.

Monteiro, Sergio Neves; Lopes, Felipe Perissé Duarte; Barbosa, Anderson Paula; Bevitori, Alice Barreto; Silva, Isabela Leão Amaral Da; Costa, Lucas Lopes Da

2011-10-01

319

Natural Frequencies of Composite Cylindrical Helical Springs Under Compression  

NASA Astrophysics Data System (ADS)

The governing equations of cylindrical isotropic helical springs loaded axially are extended to the study of free vibration of such helices made of composite materials. Stiffness method is used based on the first order shear deformation theory. A helical element has six degrees of freedom at each node, three translations and three rotations. The element stiffness matrix is obtained exactly based on the both complementary functions and the transfer matrix methods.

Kacar, ?lyas; Yildirim, Vebil

320

Predictors of clinical wear of restorative dental composite materials.  

PubMed

The mode-I plane-strain fracture toughness values of eight posterior restorative composite materials were determined using straight-sided chevron-notch short-rod specimens and a special loading module. These results, together with the values of the modulus of elasticity, modulus of resilience, and flexural strength of these materials (as given in a paper by a previous worker) were used in a detailed correlational exercise, with the values of the clinical wear of restorations made from these materials (as given in the aforementioned paper) being the dependent variable. It was found that clinical wear may best be predicted using values of all four aforementioned mechanical properties. PMID:8193568

Lewis, G

1993-01-01

321

Strength criteria for composite materials (a literature survey)  

NASA Technical Reports Server (NTRS)

Literature concerning strength (failure) criteria for composite materials is reviewed with emphasis on phenomenological failure criteria. These criteria are primarily intended to give a good estimation of the safety margin with respect to failure for arbitrary multiaxial stress states. The failure criteria do not indicate the types of fracture that will occur in the material. The collection of failure criteria is evaluated for applicability for the glass reinforced plastics used in mine detectors. Material tests necessary to determine the parameters in the failure criteria are discussed.

Roode, F.

1982-01-01

322

Modular design in natural and biomimetic soft materials.  

PubMed

Under eons of evolutionary and environmental pressure, biological systems have developed strong and lightweight peptide-based polymeric materials by using the 20 naturally occurring amino acids as principal monomeric units. These materials outperform their man-made counterparts in the following ways: 1) multifunctionality/tunability, 2) adaptability/stimuli-responsiveness, 3) synthesis and processing under ambient and aqueous conditions, and 4) recyclability and biodegradability. The universal design strategy that affords these advanced properties involves "bottom-up" synthesis and modular, hierarchical organization both within and across multiple length-scales. The field of "biomimicry"-elucidating and co-opting nature's basic material design principles and molecular building blocks-is rapidly evolving. This Review describes what has been discovered about the structure and molecular mechanisms of natural polymeric materials, as well as the progress towards synthetic "mimics" of these remarkable systems. PMID:21898722

Kushner, Aaron M; Guan, Zhibin

2011-09-19

323

Future trends in advanced fibers and composite materials technology  

SciTech Connect

By drawing on the wealth of new knowledge in advanced materials, bioscience, and information science, advanced fiber and composite systems are entering a new phase of development. Advances in the understanding of structure/property relationships of materials and related processing technologies have made it possible to tailor-make new material systems, molecule by molecule, to meet specific engineering needs better than metals. The theoretical limits for strength and stiffness of fibers can be predicted based on bond strength and cohesive forces. In the future, fiber technology will continue to advance toward achieving fiber properties closer to theoretical, increasing chemical stability, and developing new product forms tailored for specific engineering needs. The development of tailored high performance fibers and resins systems combined with advances in enabling technologies will provide most efficient solutions to engineering problems. In the future, self-monitoring and self-correcting ``smart`` composite systems will not only sense their structural environment but also respond to prevent structural failures. Just as man-made fibers revolutionized what people wear, man-made composite material systems will revolutionize how people design and build structural material systems.

Dhingra, A.K.; Doherty, T.P. [DuPont, Wilmington, DE (United States)

1993-12-31

324

Investigation of low velocity impact damage on filamentary composite materials  

NASA Technical Reports Server (NTRS)

Presented are the results of an investigation of the effect of low velocity impact on the residual modulus and residual strength of flat filamentary composite materials. Theoretical analysis of composite materials indicates that the modulus of the material must decrease as impact damage increases. This decrease must also correlate to the decrease in residual strength. This study attempts to verify these hypotheses. Graphite/epoxy laminates (AS4/3501-6) of various fiber orientations (8 (0 deg), 2 (+ or - 45 deg)sub 8) were impacted using a falling weight impact tester. Impact energies ranged from 0.42 to 1.55 ft-lb, with impact velocities from 2.03 to 3.98 ft/sec. The results show that there is a reduction in residual modulus of the plate as the impact energy increases.

Bower, Mark V.

1987-01-01

325

High resolution computed tomography of advanced composite and ceramic materials  

NASA Technical Reports Server (NTRS)

Advanced composite and ceramic materials are being developed for use in many new defense and commercial applications. In order to achieve the desired mechanical properties of these materials, the structural elements must be carefully analyzed and engineered. A study was conducted to evaluate the use of high resolution computed tomography (CT) as a macrostructural analysis tool for advanced composite and ceramic materials. Several samples were scanned using a laboratory high resolution CT scanner. Samples were also destructively analyzed at the locations of the scans and the nondestructive and destructive results were compared. The study provides useful information outlining the strengths and limitations of this technique and the prospects for further research in this area.

Yancey, R. N.; Klima, S. J.

1991-01-01

326

Materials and processes laboratory composite materials characterization task, part 1. Damage tolerance  

NASA Technical Reports Server (NTRS)

A test run was performed on IM6/3501-6 carbon-epoxy in which the material was processed, machined into specimens, and tested for damage tolerance capabilities. Nondestructive test data played a major role in this element of composite characterization. A time chart was produced showing the time the composite material spent within each Branch or Division in order to identify those areas which produce a long turnaround time. Instrumented drop weight testing was performed on the specimens with nondestructive evaluation being performed before and after the impacts. Destructive testing in the form of cross-sectional photomicrography and compression-after-impact testing were used. Results show that the processing and machining steps needed to be performed more rapidly if data on composite material is to be collected within a reasonable timeframe. The results of the damage tolerance testing showed that IM6/3501-6 is a brittle material that is very susceptible to impact damage.

Nettles, A. T.; Tucker, D. S.; Patterson, W. J.; Franklin, S. W.; Gordon, G. H.; Hart, L.; Hodge, A. J.; Lance, D. G.; Russel, S. S.

1991-01-01

327

Stress and Damage in Polymer Matrix Composite Materials Due to Material Degradation at High Temperatures  

NASA Technical Reports Server (NTRS)

This report describes analytical methods for calculating stresses and damage caused by degradation of the matrix constituent in polymer matrix composite materials. Laminate geometry, material properties, and matrix degradation states are specified as functions of position and time. Matrix shrinkage and property changes are modeled as functions of the degradation states. The model is incorporated into an existing composite mechanics computer code. Stresses, strains, and deformations at the laminate, ply, and micro levels are calculated, and from these calculations it is determined if there is failure of any kind. The rationale for the model (based on published experimental work) is presented, its integration into the laminate analysis code is outlined, and example results are given, with comparisons to existing material and structural data. The mechanisms behind the changes in properties and in surface cracking during long-term aging of polyimide matrix composites are clarified. High-temperature-material test methods are also evaluated.

McManus, Hugh L.; Chamis, Christos C.

1996-01-01

328

Advanced numerical models and material characterisation techniques for composite materials subject to impact and shock wave loading  

Microsoft Academic Search

The development and validation of an advanced material model for orthotropic materials, such as fibre reinforced composites, is described. The model is specifically designed to facilitate the numerical simulation of impact and shock wave propagation through orthotropic materials and the prediction of subsequent material damage. Initial development of the model concentrated on correctly representing shock wave propagation in composite materials

R. A. Clegg; D. M. White; C. Hayhurst; W. Ridel; W. Harwick; S. Hiermaier

2003-01-01

329

A Study of Failure Criteria of Fibrous Composite Materials  

NASA Technical Reports Server (NTRS)

The research described in this paper is focused on two areas: (1) evaluation of existing composite failure criteria in the nonlinear, explicit transient dynamic finite element code, MSC.Dytran, and (2) exploration of the possibilities for modification of material and failure models to account for large deformations, progressive failure, and interaction of damage accumulation with stress/strain response of laminated composites. Following a review of the MSC.Dytran user manual, a bibliographical review of existing failure criteria of composites was performed. The papers considered most interesting for the objective of this report are discussed in section 2. The failure criteria included in the code under consideration are discussed in section 3. A critical summary of the present procedures to perform analysis and design of composites is presented in section 4. A study of the most important historical failure criteria for fibrous composite materials and some of the more recent modifications proposed were studied. The result of this analysis highlighted inadequacies in the existing failure criteria and the need to perform some numerical analyses to elucidate the answer to questions on which some of the proposed criteria are based. A summary of these ideas, which is a proposal of studies to be developed, is presented in section 5. Finally, some ideas for future developments are summarized in section 6.

Paris, Federico; Jackson, Karen E. (Technical Monitor)

2001-01-01

330

Dual-nanoparticulate-reinforced aluminum matrix composite materials  

NASA Astrophysics Data System (ADS)

Aluminum (Al) matrix composite materials reinforced with carbon nanotubes (CNT) and silicon carbide nanoparticles (nano-SiC) were fabricated by mechanical ball milling, followed by hot-pressing. Nano-SiC was used as an active mixing agent for dispersing the CNTs in the Al powder. The hardness of the produced composites was dramatically increased, up to eight times higher than bulk pure Al, by increasing the amount of nano-SiC particles. A small quantity of aluminum carbide (Al4C3) was observed by TEM analysis and quantified using x-ray diffraction. The composite with the highest hardness values contained some nanosized Al4C3. Along with the CNT and the nano-SiC, Al4C3 also seemed to play a role in the enhanced hardness of the composites. The high energy milling process seems to lead to a homogeneous dispersion of the high aspect ratio CNTs, and of the nearly spherical nano-SiC particles in the Al matrix. This powder metallurgical approach could also be applied to other nanoreinforced composites, such as ceramics or complex matrix materials.

Kwon, Hansang; Cho, Seungchan; Leparoux, Marc; Kawasaki, Akira

2012-06-01

331

Electronic materials high-T(sub c) superconductivity polymers and composites structural materials surface science and catalysts industry participation  

NASA Technical Reports Server (NTRS)

The fifth year of the Center for Advanced Materials was marked primarily by the significant scientific accomplishments of the research programs. The Electronics Materials program continued its work on the growth and characterization of gallium arsenide crystals, and the development of theories to understand the nature and distribution of defects in the crystals. The High Tc Superconductivity Program continued to make significant contributions to the field in theoretical and experimental work on both bulk materials and thin films and devices. The Ceramic Processing group developed a new technique for cladding YBCO superconductors for high current applications in work with the Electric Power Research Institute. The Polymers and Composites program published a number of important studies involving atomistic simulations of polymer surfaces with excellent correlations to experimental results. The new Enzymatic Synthesis of Materials project produced its first fluorinated polymers and successfully began engineering enzymes designed for materials synthesis. The structural Materials Program continued work on novel alloys, development of processing methods for advanced ceramics, and characterization of mechanical properties of these materials, including the newly documented characterization of cyclic fatigue crack propagation behavior in toughened ceramics. Finally, the Surface Science and Catalysis program made significant contributions to the understanding of microporous catalysts and the nature of surface structures and interface compounds.

1988-01-01

332

Processing- structure- property relationship in needle punched nonwoven natural fiber mat composites.  

E-print Network

??Natural fibers, such as hemp and flax, are emerging as cheaper reinforcing fibers for polymer composites. Renew-ability, comparable specific properties, and biodegradability make natural fibers… (more)

Fahimian, Mahboobeh

2013-01-01

333

Test Report: Direct and Indirect Lightning Effects on Composite Materials  

NASA Technical Reports Server (NTRS)

Lightning tests were performed on composite materials as a part of an investigation of electromagnetic effects on the materials. Samples were subjected to direct and remote simulated lightning strikes. Samples included various thicknesses of graphite filament reinforced plastic (GFRP), material enhanced by expanded aluminum foil layers, and material with an aluminum honeycomb core. Shielding properties of the material and damage to the sample surfaces and joints were investigated. Adding expanded aluminum foil layers and increasing the thickness of GFRP improves the shielding effectiveness against lightning induced fields and the ability to withstand lightning strikes. A report describing the lightning strike tests performed by the U.S. Army Redstone Technical Test Center, Redstone Arsenal, AL, STERT-TE-E-EM, is included as an appendix.

Evans, R. W.

1997-01-01

334

The weak interfaces within tough natural composites: experiments on three types of nacre.  

PubMed

Mineralization is a typical strategy used in natural materials to achieve high stiffness and hardness for structural functions such as skeletal support, protection or predation. High mineral content generally leads to brittleness, yet natural materials such as bone, mollusk shells or glass sponge achieve relatively high toughness considering the weakness of their constituents through intricate microstructures. In particular, nanometers thick organic interfaces organized in micro-architectures play a key role in providing toughness by various processes including crack deflection, crack bridging or energy dissipation. While these interfaces are critical in these materials, their composition, structure and mechanics is often poorly understood. In this work we focus on nacre, one of the most impressive hard biological materials in terms of toughness. We performed interfacial fracture tests on chevron notched nacre samples from three different species: red abalone, top shell and pearl oyster. We found that the intrinsic toughness of the interfaces is indeed found to be extremely low, in the order of the toughness of the mineral inclusions themselves. Such low toughness is required for the cracks to follow the interfaces, and to deflect and circumvent the mineral tablets. This result highlights the efficacy of toughening mechanisms in natural materials, turning low-toughness inclusions and interfaces into high-performance composites. We found that top shell nacre displayed the highest interfacial toughness, because of higher surface roughness and a more resilient organic material, and also through extrinsic toughening mechanisms including crack deflection, crack bridging and process zone. In the context of biomimetics, the main implication of this finding is that the interface in nacre-like composite does not need to be tough; the extensibility or ductility of the interfaces may be more important than their strength and toughness to produce toughness at the macroscale. PMID:23084045

Khayer Dastjerdi, Ahmad; Rabiei, Reza; Barthelat, Francois

2013-03-01

335

Elastoplastic analysis of thermal cycling: Layered materials with compositional gradients  

SciTech Connect

Elastoplastic analyses are presented for the cyclic thermal response in multi-layered materials which comprise layers of fixed compositions of a metal and a ceramic, and a compositionally graded interface. Analytical solutions for the characteristic temperature at which the onset of thermally induced plastic deformation occurs are derived for the layered composite. Solutions for the evolution of curvature and thermal strains, and for the initiation of plastic yielding are also obtained for different combinations of the geometry, physical properties and compositional gradation for both thermoelastic and thermoplastic deformation. Finite-element formulations incorporating continuous and smooth spatial variations in the composition and properties of the graded layer are used to simulate the evolution of thermal stresses, the accumulation of plastic strains, and the development of monotonic and cyclic plastic zones at the interfaces, edges and free surfaces of different layers during thermal cycling. Engineering diagrams detailing the effects of compositional gradients are also presented for optimizing thermal residual stresses, layer geometry, and plastic strain accumulation.

Giannakopulos, A.E.; Olsson, M. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid Mechanics] [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid Mechanics; Suresh, S.; Finot, M. [Massachusetts Inst. of Tech., Cambridge, MA (United States)] [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1995-04-01

336

Material and structural studies of metal and polymer matrix composites  

NASA Technical Reports Server (NTRS)

Fiber-reinforced composites and design analysis methods for these materials are being developed because of the vast potential of composites for decreasing weight and/or increasing use temperature capability in aerospace systems. These composites have potential for use in airbreathing engine components as well as aeronautical and space vehicle structures. Refractory wire-superalloy composites for use up to 2200 F or more and metal-matrix composites for lower temperature applications such as aerospace structures and turbojet fan and compressor blades are under investigation and are discussed. The development of a number of resin systems, including the polyimides and polyphenylquinoxalines, is described and their potential for use at temperatures approaching 315 C (600 F) is indicated. Various molecular modifications that improve processability and/or increase thermal and oxidative resistance of the resins are also described. Structural analysis methods are discussed for determining the stresses and deformations in complex composite systems. Consideration is also given to residual stresses resulting from the curing process and to the foreign object damage problem in fan blade applications.

Signorelli, R. A.; Serafini, T. T.; Johns, R. H.

1973-01-01

337

Contribution to the study of composite materials and their damage. Thesis - Paris VI Univ. - 1984  

NASA Technical Reports Server (NTRS)

Chapter 1 describes the homogenization techniques used for defining the overall behavior of composite materials for conventional cases of linear and perfectly glued elastic constituents. Chapters 2 and 3 focus on solving the problems inherent in two types of degenerated situations: elastic media with microcavities, and elastic media containing rigid inclusions. Through suitable definitions of deformation concepts and macroscopic stresses it is shown that conventional theory results apply naturally to these limits.

Lene, F.

1987-01-01

338

Use of natural raw material for the production of photochromic glasses  

SciTech Connect

The authors investigated the possibility of using natural raw materials as replacements for soda and alumina for obtaining photochromic glasses and to determine their properties. Glasses of the sodium aluminoborosilicate system were studied. The characteristics of the batches and some of the properties of the glasses are given in a table. Sodium oxide was added to batches Nos. 1 and 2 as soda or borax. Composition Nos. 3, 4, and 5 were prepared using acid, basic, and neutral rocks by means of which the oxides of sodium and aluminum were added. The glasses were synthesized in SiC-heater furnaces. The differential thermal analysis of compositions Nos. 1 and 5 showed that the presence of natural materials leads to the formation of a liquid phase at lower temperatures which helps to intensify the processes of silicate- and glass-formation.

Kiyan, V.I.; Artamonova, M.V.; Solinov, V.F.

1986-07-01

339

The percolation staircase model and its manifestation in composite materials  

NASA Astrophysics Data System (ADS)

We studied the tunneling percolation conductivity dependence on the site or bond occupation probability in the square lattice. The model predicts that in both, lattice and continuum systems in which there is a hierarchy of the local conductances, the dependence of the global conductivity on the site or volume occupation probability will yield a conductivity staircase. In particular we evaluate the implications of the staircase on the critical behavior of the conductivity. We then show experimental evidence for the predicted percolation-tunneling staircase in a Ag-Al2O3 granular metal system and in a carbon black-polymer composite. Following that, we propose that for carbon nanotube (CNT) polymer composites the data in the literature give ample support to a percolation-dispersion staircase behavior. The implication of the present findings on the percolation-hopping problem in composite materials is also discussed.

Balberg, I.; Azulay, D.; Goldstein, Y.; Jedrzejewski, J.; Ravid, G.; Savir, E.

2013-10-01

340

Compendium of Material Composition Data for Radiation Transport Modeling  

SciTech Connect

Introduction Meaningful simulations of radiation transport applications require realistic definitions of material composition and densities. When seeking that information for applications in fields such as homeland security, radiation shielding and protection, and criticality safety, researchers usually encounter a variety of materials for which elemental compositions are not readily available or densities are not defined. Publication of the Compendium of Material Composition Data for Radiation Transport Modeling, Revision 0, in 2006 was the first step toward mitigating this problem. Revision 0 of this document listed 121 materials, selected mostly from the combined personal libraries of staff at the Pacific Northwest National Laboratory (PNNL), and thus had a scope that was recognized at the time to be limited. Nevertheless, its creation did provide a well-referenced source of some unique or hard-to-define material data in a format that could be used directly in radiation transport calculations being performed at PNNL. Moreover, having a single common set of material definitions also helped to standardize at least one aspect of the various modeling efforts across the laboratory by providing separate researchers the ability to compare different model results using a common basis of materials. The authors of the 2006 compendium understood that, depending on its use and feedback, the compendium would need to be revised to correct errors or inconsistencies in the data for the original 121 materials, as well as to increase (per users suggestions) the number of materials listed. This 2010 revision of the compendium has accomplished both of those objectives. The most obvious change is the increased number of materials from 121 to 372. The not-so-obvious change is the mechanism used to produce the data listed here. The data listed in the 2006 document were compiled, evaluated, entered, and error-checked by a group of individuals essentially by hand, providing no library file or mechanism for revising the data in a consistent and traceable manner. The authors of this revision have addressed that problem by first compiling all of the information (i.e., numbers and references) for all the materials into a single database, maintained at PNNL, that was then used as the basis for this document.

McConn, Ronald J.; Gesh, Christopher J.; Pagh, Richard T.; Rucker, Robert A.; Williams III, Robert

2011-03-04

341

Degradation of experimental composite materials and in vitro wear simulation  

NASA Astrophysics Data System (ADS)

The material, mechanical, and clinical aspects of surface degradation of resin composite dental restorative materials by in vitro wear simulation continues to be an area of active research. To investigate wear mechanisms, a series of experimental resin composites with variable and controlled filler particle shape and loading were studied by in vitro wear simulation. The current investigation utilized a simulation that isolated the wear environment, entrapped high and low modulus debris, and evaluated the process including machine and fluid flow dynamics. The degradation was significantly affected by filler particle shape and less by particle loading. The spherical particle composites demonstrated wear loss profiles suggesting an optimized filler loading may exist. This was also demonstrated by the trends in the mechanical properties. Very little difference in magnitude was noted for the wear of irregular particle composites as a function of particulate size; and as a group they were more wear resistant than spherical particle composites. This was the result of different mechanisms of wear that were correlated with the three-dimensional particle shape. The abrasive effects of the aggregate particles and the polymeric stabilization of the irregular shape versus the destabilization and "plucking" of the spherical particles resulted in an unprotected matrix that accounted for significantly greater wear of spherical composite. A model and analysis was developed to explain the events associated with the progressive material wear loss. The initial phase was explained by fatigue-assisted microcracking and loss of material segments in a zone of high stress immediately beneath a point of high stress contact. The early phase was characterized by the development of a small facet primarily by fatigue-assisted microcracking. Although the translation effects were minimal, some three-body and initial two-body wear events were also present. In the late phases, the abrasive effects of the debris aggregate predominated the wear process. The non-linear rate of wear loss was accelerated as the facet deepened. Physical effects, such as thermal fatigue, and chemical effects were less important but contributed to the degradation process. This study provides new insight into the role(s) of high modulus third body debris in the wear of dental composites.

Givan, Daniel Allen

2001-12-01

342

Ultrasonic Characterization of Fatigue Cracks in Composite Materials  

NASA Technical Reports Server (NTRS)

Microcracking in composite structures due to combined fatigue and cryogenic loading can cause leakage and failure of the structure and can be difficult to detect in-service. In aerospace systems, these leaks may lead to loss of pressure/propellant, increased risk of explosion and possible cryo-pumping. The success of nondestructive evaluation to detect intra-ply microcracking in unlined pressure vessels fabricated from composite materials is critical to the use of composite structures in future space systems. The work presented herein characterizes measurements of intraply fatigue cracking through the thickness of laminated composite material by means of correlation with ultrasonic resonance. Resonant ultrasound spectroscopy provides measurements which are sensitive to both the microscopic and macroscopic properties of the test article. Elastic moduli, acoustic attenuation, and geometry can all be probed. The approach is based on the premise of half-wavelength resonance. The method injects a broadband ultrasonic wave into the test structure using a swept frequency technique. This method provides dramatically increased energy input into the test article, as compared to conventional pulsed ultrasonics. This relative energy increase improves the ability to measure finer details in the materials characterization, such as microcracking and porosity. As the microcrack density increases, more interactions occur with the higher frequency (small wavelength) components of the signal train causing the spectrum to shift toward lower frequencies. Several methods are under investigation to correlate the degree of microcracking from resonance ultrasound measurements on composite test articles including self organizing neural networks, chemometric techniques used in optical spectroscopy and other clustering algorithms.

Workman, Gary L.; Watson, Jason; Johnson, Devin; Walker, James; Russell, Sam; Thom, Robert (Technical Monitor)

2002-01-01

343

DOE/MSU composite material fatigue database: Test methods, materials, and analysis  

SciTech Connect

This report presents a detailed analysis of the results from fatigue studies of wind turbine blade composite materials carried out at Montana State University (MSU) over the last seven years. It is intended to be used in conjunction with the DOE/MSU composite Materials Fatigue Database. The fatigue testing of composite materials requires the adaptation of standard test methods to the particular composite structure of concern. The stranded fabric E-glass reinforcement used by many blade manufacturers has required the development of several test modifications to obtain valid test data for materials with particular reinforcement details, over the required range of tensile and compressive loadings. Additionally, a novel testing approach to high frequency (100 Hz) testing for high cycle fatigue using minicoupons has been developed and validated. The database for standard coupon tests now includes over 4,100 data points for over 110 materials systems. The report analyzes the database for trends and transitions in static and fatigue behavior with various materials parameters. Parameters explored are reinforcement fabric architecture, fiber content, content of fibers oriented in the load direction, matrix material, and loading parameters (tension, compression, and reversed loading). Significant transitions from good fatigue resistance to poor fatigue resistance are evident in the range of materials currently used in many blades. A preliminary evaluation of knockdowns for selected structural details is also presented. The high frequency database provides a significant set of data for various loading conditions in the longitudinal and transverse directions of unidirectional composites out to 10{sup 8} cycles. The results are expressed in stress and strain based Goodman Diagrams suitable for design. A discussion is provided to guide the user of the database in its application to blade design.

Mandell, J.F.; Samborsky, D.D. [Montana State Univ., Bozeman, MT (United States). Dept. of Chemical Engineering

1997-12-01

344

Carbonization of wood at 400°C for composite materials  

NASA Astrophysics Data System (ADS)

The carbonization process for large pieces of wood was investigated to produce a solid carbonized wood skeleton precursor that retains the cellular structure of the wood without the formation of cracks and with reduced longitudinal deformation. Two carbonization schedules were designed for the conversion of sugar maple (Acer saccharum) and southern pine ( Pinus spp) into amorphous carbon at a heat treatment temperature of 400°C. Samples from commercial lumber were carbonized to produce the materials. Each schedule was designed meticulously through DTA-TGA for each wood species. The materials were characterized by their average yields, dimensional changes, density, porosity, SEM and mechanical testing. Also, the materials were used as solid carbon skeletons for making resin-infused carbon composites. Structural epoxy resin was infused into the carbon material template and cured at a maximum temperature of 125°C. The depth of the resin infusion was assessed by SEM examination and the retention was analyzed by total weight gain. The strength and the stiffness of the composite materials were evaluated through mechanical testing. It was demonstrated that southern pine and sugar maple should require different heat treatment schedules for carbonization. The schedules were able to reduce the longitudinal deformation and to keep the final products free of cracks. The yield averaged around 28% for both southern pine and sugar maple. Carbonized southern pine exhibited lower density and higher porosity than carbonized sugar maple. The resin treatment increased specific gravity of carbonized materials by 9.6% and 11.6% for maple and southern pine respectively. The resin infusion improved the average MOR values by 140% and 275%. MOE of the composites was similar to that of pure epoxy.

Randrianarisoa, Bernard Laurent

345

Magnetic sensor for high temperature using a laminate composite of magnetostrictive material and piezoelectric material  

NASA Astrophysics Data System (ADS)

A high sensitive and heat-resistive magnetic sensor using a magnetostrictive/piezoelectric laminate composite is investigated. The sensing principle is based on the magnetostrictive- and piezoelectric effect, whereby a detected yoke displacement is transduced into a voltage on the piezoelectric materials. The sensor is intended to detect the displacement of a ferromagnetic object in a high temperature environment, where conventional magnetic sensors are not useful. Such applications include sensors in engine of automobile and machinery used in material processing. The sensor features combination of a laminate composite of magnetostrictive/piezoelectric materials with high Curie temperatures and an appropriate magnetic circuit to convert mechanical displacement to sensor voltages and suppress temperature fluctuation. This paper describes the sensing principle and shows experimental results using a composite of Terfenol-D and Lithium Niobate to assure high sensitivity of 50V/mm at bias gap of 0.1mm and a temperature operating range over 200 °C.

Ueno, Toshiyuki; Higuchi, Toshiro

2005-05-01

346

Natural-fiber-reinforced polymer composites in automotive applications  

NASA Astrophysics Data System (ADS)

In the past decade, natural-fiber composites with thermoplastic and thermoset matrices have been embraced by European car manufacturers and suppliers for door panels, seat backs, headliners, package trays, dashboards, and interior parts. Natural fibers such as kenaf, hemp, flax, jute, and sisal offer such benefits as reductions in weight, cost, and CO2, less reliance on foreign oil sources, and recyclability. However, several major technical considerations must be addressed before the engineering, scientific, and commercial communities gain the confidence to enable wide-scale acceptance, particularly in exterior parts where a Class A surface finish is required. Challenges include the homogenization of the fiber's properties and a full understanding of the degree of polymerization and crystallization, adhesion between the fiber and matrix, moisture repellence, and flame-retardant properties, to name but a few.

Holbery, James; Houston, Dan

2006-11-01

347

Flight simulation testing equipment for composite material systems  

NASA Technical Reports Server (NTRS)

A test program is discussed which aims at establishing the time-temperature-stress characteristics of several classes of high-temperature composite materials in order to determine their suitability for applications in supersonic cruise aircraft. Five advanced composite materials (a boron epoxy, a boron polyimide, a graphite epoxy, a graphite polyimide, and diffusion-bonded boron aluminum) are being evaluated using a flight-test simulator capable of long-term automatic testing based on random loading and realistic flight temperature profiles. The design, construction, and checkout of this simulator are described along with the digital load programmer, load magnitude controllers, the hydraulic pumping system, the heating and cooling systems, the control console, and the data recording system. Typical results for short-term tests performed at constant temperatures and accelerated load rates are presented in terms of a random-load spectrum and a wearout model.

Haskins, J. F.; Wilkins, D. J.; Stein, B. A.

1976-01-01

348

Experimental and Analytical Characterization of the Macromechanical Response for Triaxial Braided Composite Materials  

NASA Technical Reports Server (NTRS)

Increasingly, carbon composite structures are being used in aerospace applications. Their highstrength, high-stiffness, and low-weight properties make them good candidates for replacing many aerospace structures currently made of aluminum or steel. Recently, many of the aircraft engine manufacturers have developed new commercial jet engines that will use composite fan cases. Instead of using traditional composite layup techniques, these new fan cases will use a triaxially braided pattern, which improves case performance. The impact characteristics of composite materials for jet engine fan case applications have been an important research topic because Federal regulations require that an engine case be able to contain a blade and blade fragments during an engine blade-out event. Once the impact characteristics of these triaxial braided materials become known, computer models can be developed to simulate a jet engine blade-out event, thus reducing cost and time in the development of these composite jet engine cases. The two main problems that have arisen in this area of research are that the properties for these materials have not been fully determined and computationally efficient computer models, which incorporate much of the microscale deformation and failure mechanisms, are not available. The research reported herein addresses some of the deficiencies present in previous research regarding these triaxial braided composite materials. The current research develops new techniques to accurately quantify the material properties of the triaxial braided composite materials. New test methods are developed for the polymer resin composite constituent and representative composite coupons. These methods expand previous research by using novel specimen designs along with using a noncontact measuring system that is also capable of identifying and quantifying many of the microscale failure mechanisms present in the materials. Finally, using the data gathered, a new hybrid micromacromechanical computer model is created to simulate the behavior of these composite material systems under static and ballistic impact loading using the test data acquired. The model also quantifies the way in which the fiber/matrix interface affects material response under static and impact loading. The results show that the test methods are capable of accurately quantifying the polymer resin under a variety of strain rates and temperature for three loading conditions. The resin strength and stiffness data show a clear rate and temperature dependence. The data also show the hydrostatic stress effects and hysteresis, all of which can be used by researchers developing composite constitutive models for the resins. The results for the composite data reveal noticeable differences in strength, failure strain, and stiffness in the different material systems presented. The investigations into the microscale failure mechanisms provide information about the nature of the different material system behaviors. Finally, the developed computer model predicts composite static strength and stiffness to within 10 percent of the gathered test data and also agrees with composite impact data, where available.

Littell, Justin D.

2013-01-01

349

The dynamic inelastic behavior in fiber reinforced composite materials  

SciTech Connect

Accurately simulating the complete dynamic behavior, elastic and inelastic, of engineering structures composed of fiber reinforced composite materials can be accomplished by integrating three components: (1) a physically based micromechanical material model that accounts for the experimentally observed mechanisms producing the inelastic behavior; (2) a dynamic three-dimensional continuum simulation capability in which the physically based micromechanical material model is incorporated; and (3) a complete set of robust dynamic experiments. These experiments are used (1) to establish the microstructural mechanisms that produce inelastic behavior and (2) to validate the dynamic simulation capability. This paper focuses on the implementation of a physically based micromechanical material model into an explicit 3D finite element code and shows the experimental comparison.

Haberman, K.S.; Bennett, J.G.; Liu, Cheng [and others

1997-03-01

350

Intermetallic and titanium matrix composite materials for hypersonic applications  

SciTech Connect

As part of the French Program of Research and Technology for Advanced Hypersonic Propulsion (PREPHA) which was launched in 1992 between Aerospatiale, Dassault Aviation, ONERA, SNECMA and SEP, an important work is specially devoted to the development of titanium and intermetallic composite materials for large airframe structures. At Dassault Aviation, starting from a long experience in Superplastic Forming - Diffusion Bonding (SPF-DB) of titanium parts, the effort is brought on the manufacturing and characterization of composites made from Timet beta 21S or IMI 834 foils and Textron SCS6 fiber fabrics. At `Aersopatiale Espace & Defence`, associated since a long time about intermetallic composite materials with university research laboratories, the principal effort is brought on plasma technology to develop the gamma titanium aluminide TiAl matrix composite reinforced by protected silicon carbide fibers (BP SM 1240 or TEXTRON SCS6). The objective, is to achieve, after 3 years of time, to elaborate a medium size integrally stiffened panel (300 x 600 sq mm).

Berton, B.; Surdon, G.; Colin, C. [Dassault Aviation, Saint-Cloud (France)]|[Aersopatiale Space & Defence, St Medard en Jalles (France)

1995-09-01

351

Conducting polymer composite materials for smart microwave windows  

NASA Astrophysics Data System (ADS)

Samples of poly(aniline)-silver-polymer electrolyte particulate composites have been characterized at microwave frequencies when small d.c. electric fields are applied across them in both coaxial line and waveguide measurement test sets. The experimental data shows that the initial conductivity of the materials is dependent on the concentration of sliver metal and suggest that changes in resistance due to chemical switching take place, at least in part, in the manufacture of the composites. When silver is used as the electrodes, the experimental data show that changes in the slope of the cyclic voltammograms coincide with large changes in microwave reflectivity or transmission consistent with increasing conductivity of the composites when fields are applied. The reverse change occurs when the fields are removed. Measurements have shown that the composites are able to switch between the two impedance stats in times of less than one second for well over a million cycles with no apparent depreciation in material properties. Large area films have also been prepared and studied using the 'free space' technique.

Barnes, Alan; Lees, K.; Wright, Peter V.; Chambers, Barry

1999-07-01

352

Materials and Process Activities for NASA's Composite Crew Module  

NASA Technical Reports Server (NTRS)

In January 2007, the NASA Administrator and Associate Administrator for the Exploration Systems Mission Directorate chartered the NASA Engineering and Safety Center (NESC) to design, build, and test a full-scale Composite Crew Module (CCM). The overall goal of the CCM project was to develop a team from the NASA family with hands-on experience in composite design, manufacturing, and testing in anticipation of future space exploration systems being made of composite materials. The CCM project was planned to run concurrently with the Orion project s baseline metallic design within the Constellation Program so that features could be compared and discussed without inducing risk to the overall Program. The materials and process activities were prioritized based on a rapid prototype approach. This approach focused developmental activities on design details with greater risk and uncertainty, such as out-of-autoclave joining, over some of the more traditional lamina and laminate building block levels. While process development and associated building block testing were performed, several anomalies were still observed at the full-scale level due to interactions between process robustness and manufacturing scale-up. This paper describes the process anomalies that were encountered during the CCM development and the subsequent root cause investigations that led to the final design solutions. These investigations highlight the importance of full-scale developmental work early in the schedule of a complex composite design/build project.

Polis, Daniel L.

2012-01-01

353

Probability techniques for reliability analysis of composite materials  

NASA Technical Reports Server (NTRS)

Traditional design approaches for composite materials have employed deterministic criteria for failure analysis. New approaches are required to predict the reliability of composite structures since strengths and stresses may be random variables. This report will examine and compare methods used to evaluate the reliability of composite laminae. The two types of methods that will be evaluated are fast probability integration (FPI) methods and Monte Carlo methods. In these methods, reliability is formulated as the probability that an explicit function of random variables is less than a given constant. Using failure criteria developed for composite materials, a function of design variables can be generated which defines a 'failure surface' in probability space. A number of methods are available to evaluate the integration over the probability space bounded by this surface; this integration delivers the required reliability. The methods which will be evaluated are: the first order, second moment FPI methods; second order, second moment FPI methods; the simple Monte Carlo; and an advanced Monte Carlo technique which utilizes importance sampling. The methods are compared for accuracy, efficiency, and for the conservativism of the reliability estimation. The methodology involved in determining the sensitivity of the reliability estimate to the design variables (strength distributions) and importance factors is also presented.

Wetherhold, Robert C.; Ucci, Anthony M.

1994-01-01

354

Characterization of carbon fiber composite materials for RF applications  

NASA Astrophysics Data System (ADS)

Carbon Fiber Composite (CFC) materials have been used for decades in the aerospace, automotive, and naval industries. They have often been used because of their mechanical advantages. These advantageous characteristics have typically included low weight and high strength. It is also a benefit that CFC materials can be made into nearly any shape or size. With the abundant use of CFC materials, it seems desirable to better under- stand the electromagnetic applications of these materials. CFC materials consist of a non-conductive resin or epoxy in addition to conductive carbon fibers. The carbon fibers can be oriented and layered in many different configurations. The specific orientation and layering of the carbon fibers has a direct impact on its electrical characteristics. One specific characteristic of interest is the conductivity of CFC materials. The work in this paper deals with probing the conductivity characteristics of CFC materials for applications in antenna and radar design. Multiple layouts of carbon fiber are investigated. The DC conductivity was measured by applying a conductive epoxy to sample edges and using a milliohm meter. Shielding effectiveness was then predicted based on fundamental electromagnetics for conducting media. Finally, prototype dipole antennas made from CFC materials were investigated.

Riley, Elliot J.; Lenzing, Erik H.; Narayanan, Ram M.

2014-05-01

355

Nanocrystal-Based Polymer Composites as Novel Functional Materials  

Microsoft Academic Search

\\u000a This chapter provides an overall picture of nanocrystal-polymer based composites and describes the key properties of these\\u000a original functional materials, particularly suited for advanced applications in photonic, optoelectronic as well as in sensing.\\u000a Here, we aim at pointing out the relevance of the incorporation of inorganic colloidal nanocrystals with size-dependent properties\\u000a in highly processable polymers. Due to the countless different

M. Striccoli; M. L. Curri; R. Comparelli

356

Development of active composites using conventional structural materials  

Microsoft Academic Search

Development of new active composites using conventional structural materials are described in this paper. An active CFRP\\/Al laminate was proposed and developed, which became flat when it was kept at its hot pressing temperature 393K by electric resistance heating of the carbon fiber in the CFRP layer, and its curvature increased when it was air-cooled. The mechanism of its actuation

Hiroshi Asanuma; Osamu Haga; Genji Hakoda; Junichiro Ohira

2001-01-01

357

Application of fictitious domain method to analysis of composite materials  

Microsoft Academic Search

A method that allows one to solve general three-dimensional nonlinear problems arising in the micromechanics of composite materials is introduced. The principal idea of the method is to replace a boundary-value problem defined on a complicated domain by a set of boundary-value problems defined on simple domains. This replacement allows one to avoid complicated mesh generation and to exploit fast

Eugene Grigorievich Podnos

1999-01-01

358

Manganese oxide–carbon composite as supercapacitor electrode materials  

Microsoft Academic Search

Nano-sized manganese oxide (Mn2O3) was incorporated homogeneously in templated mesoporous carbon to prepare Mn2O3–carbon nanocomposites, which were used as supercapacitor electrodes. Cyclic voltammetry was employed to investigate the electrochemical properties of the composite materials in an aqueous electrolyte under different scan rates. Results showed that templated mesoporous carbon with layered graphene domains holds a great promise for high-rate supercapacitor applications.

Li Li Zhang; Tianxin Wei; Wenjuan Wang; X. S. Zhao

2009-01-01

359

Degradation, Fatigue, and Failure of Resin Dental Composite Materials  

Microsoft Academic Search

The intent of this article is to review the numerous factors that affect the mechanical properties of particle-or fiber-filler-containing indirect dental resin composite materials. The focus will be on the effects of degradation due to aging in different media, mainly water and water and ethanol, cyclic loading, and mixed-mode loading on flexure strength and fracture toughness. Several selected papers will

J. L. Drummond

2008-01-01

360

Mechanical response of a mine composite material to extreme heat  

Microsoft Academic Search

The use of cemented paste backfills (CPB, a mine composite tailings material) in underground mining is currently increasing\\u000a in importance globally. However, despite the tremendous progress made in understanding the factors affecting the performance\\u000a of CPB, little attention has been devoted to the impact of high temperatures on its mechanical properties. This article presents\\u000a the results of experimental investigations into

L. Orejarena; M. Fall

2008-01-01

361

Non-destructive evaluation of composite materials using ultrasound  

NASA Technical Reports Server (NTRS)

Investigation of the nondestructive evaluation of advanced composite-laminates is summarized. Indices derived from the measurement of fundamental acoustic parameters are used in order to quantitatively estimate the local material properties of the laminate. The following sections describe ongoing studies of phase insensitive attenuation measurements, and discuss several phenomena which influences the previously reported technique of polar backscatter. A simple and effective programmable gate circuit designed for use in estimating attenuation from backscatter is described.

Miller, J. G.

1984-01-01

362

Facesheet Delamination of Composite Sandwich Materials at Cryogenic Temperatures  

NASA Technical Reports Server (NTRS)

The next generation of space transportation vehicles will require advances in lightweight structural materials and related design concepts to meet the increased demands on performance. One potential source for significant structural weight reduction is the replacement of traditional metallic cryogenic fuel tanks with new designs for polymeric matrix composite tanks. These new tank designs may take the form of thin-walled sandwich constructed with lightweight core and composite facesheets. Life-time durability requirements imply the materials must safely carry pressure loads, external structural loads, resist leakage and operate over an extremely wide temperature range. Aside from catastrophic events like tank wall penetration, one of the most likely scenarios for failure of a tank wall of sandwich construction is the permeation of cryogenic fluid into the sandwich core and the subsequent delamination of the sandwich facesheet due to the build-up of excessive internal pressure. The research presented in this paper was undertaken to help understand this specific problem of core to facesheet delamination in cryogenic environments and relate this data to basic mechanical properties. The experimental results presented herein provide data on the strain energy release rate (toughness) of the interface between the facesheet and the core of a composite sandwich subjected to simulated internal pressure. A unique test apparatus and associated test methods are described and the results are presented to highlight the effects of cryogenic temperature on the measured material properties.

Gates, Thomas S.; Odegard, Gregory M.; Herring, Helen M.

2003-01-01

363

The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials  

NASA Technical Reports Server (NTRS)

During the past three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. As part of my startup package I received funds to construct a state-of-the-art experimental facility to study gas-solid reaction kinetics. Much of our effort was spent developing the methodology to measure the abundance and isotopic composition of Hg at ultratrace levels in solid materials. In our first study, the abundance and isotopic composition of Hg was determined in bulk samples of the Murchison (CM) and Allende (CV) carbonaceous chondrites. We have continued our study of mercury in primitive meteorites and expanded the suite of meteorites to include other members of the CM and CV chondrite group as well as CI and CO chondrites. Samples of the CI chondrite Orgueil, the CM chondrites Murray, Nogoya, and Cold Bokkeveld, the CO chondrites Kainsaz, Omans, and Isna, and the CV chondrites Vigarano, Mokoia, and Grosnaja were tested. We have developed a thermal analysis ICP-MS technique and applied it to the study of a suite of thermally labile elements (Zn, As, Se, Cd, In, Sn, Sb, Te, Hg, Au, Tl, Pb, and Bi) in geologic materials as well.

Lauretta, D. S.

2004-01-01

364

Characterization of Triaxial Braided Composite Material Properties for Impact Simulation  

NASA Technical Reports Server (NTRS)

The reliability of impact simulations for aircraft components made with triaxial braided carbon fiber composites is currently limited by inadequate material property data and lack of validated material models for analysis. Improvements to standard quasi-static test methods are needed to account for the large unit cell size and localized damage within the unit cell. The deformation and damage of a triaxial braided composite material was examined using standard quasi-static in-plane tension, compression, and shear tests. Some modifications to standard test specimen geometries are suggested, and methods for measuring the local strain at the onset of failure within the braid unit cell are presented. Deformation and damage at higher strain rates is examined using ballistic impact tests on 61- by 61- by 3.2-mm (24- by 24- by 0.125-in.) composite panels. Digital image correlation techniques were used to examine full-field deformation and damage during both quasi-static and impact tests. An impact analysis method is presented that utilizes both local and global deformation and failure information from the quasi-static tests as input for impact simulations. Improvements that are needed in test and analysis methods for better predictive capability are examined.

Roberts, Gary D.; Goldberg, Robert K.; Biniendak, Wieslaw K.; Arnold, William A.; Littell, Justin D.; Kohlman, Lee W.

2009-01-01

365

Strain Gage Selection Criteria for Textile Composite Materials  

NASA Technical Reports Server (NTRS)

This report will provide a review of efforts to establish a set of strain gage selection guidelines for textile reinforced composite materials. A variety of strain gages were evaluated in the study to determine the sensitivity of strain measurements to the size of the strain gage. The strain gages were chosen to provide a range of gage lengths and widths. The gage aspect ratio (the length-to-width ratio) was also varied. The gages were tested on a diverse collection of textile composite laminates. Test specimens featured eleven different textile architectures: four 2-D triaxial braids, six 3-D weaves, and one stitched uniweave architecture. All specimens were loaded in uniaxial tension. The materials' moduli were measured in both the longitudinal (parallel to the O deg. yarns) and the transverse (perpendicular to the O deg. yarns) directions. The results of these measurements were analyzed to establish performance levels for extensometers and strain gages on textile composite materials. Conclusions are expressed in a summary that discusses instrumentation practices and defines strain gage selection criteria.

Masters, John E.

1996-01-01

366

Infrared Spectroscopic Identification of Chosen Dental Materials and Natural Teeth  

NASA Astrophysics Data System (ADS)

Studies using solid phase infrared spectroscopy in the range of 400 to 4000 wave numbers were conducted in order to quickly identify solid tooth fragments and differentiate them from dental materials used in the dental practice. The frequently employed dental materials were evaluated. Natural chemical structure of permanent teeth obtained from donors of various ages provided the reference material. The infrared vibrations detected in infrared transmission spectra depended on the chemical structure of examined compound. Comparable distinctive peaks in infrared spectra of natural teeth and inorganic dental materials (porcelain) were exhibited. Analogous infrared spectra of dental materials consisting of organic matrix with inorganic fillers were found. In the case of acrylic materials specific organic groups were enhanced. The prepared database of infrared transmission spectra included 23 dental materials, facilitating their appropriate identification. Application of infrared spectroscopy allowed for a quick differential identification of typical dental materials produced from organic compounds for inorganic restorations (porcelain) and of tooth structure-resembling hydroxyapatite and its contaminate forms with fluoride and carbonate ions.

H?dzelek, W.; Marcinkowska, A.; Domka, L.; Wachowiak, R.

2008-08-01

367

Preparation of conductive paper composites based on natural cellulosic fibers for packaging applications.  

PubMed

Conducting paper based on natural cellulosic fibers and conductive polymers was prepared using unbleached bagasse and/or rice straw fibers (as cellulosic raw materials) and polyaniline (PANi) as conducting polymer. These composites were synthesized by in situ emulsion polymerization using ammonium persulfate (APS) as oxidant in the presence of dodecylbenzene sulfonic acid (DBSA) as emulsifier. The prepared composites were characterized using Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC), and their morphology was investigated using scanning electron microscope (SEM). Electrical conductivity measurements showed that the conductivity of the paper sheets increases by increasing the ratio of PANi in the composite. Mechanical properties of the paper sheets were also investigated, the results revealed that the values of breaking length, burst factor, and tear factor are decreased with increasing ratio of added PANi, and this effect is more pronounced in bagasse-based composites. The new conductive composites can have potential use as anti-static packaging material or anti-bacterial paper for packaging applications. PMID:24750909

Youssef, Ahmed M; El-Samahy, Magda Ali; Abdel Rehim, Mona H

2012-08-01

368

Bioactivity and phenolic composition from natural fermented table olives.  

PubMed

In the present work, the phenolic composition, and antioxidant and antimicrobial properties of twenty-four samples of naturally fermented table olives from the northeast of Portugal were evaluated. The analysis of phenolic composition was performed by HPLC/DAD, and ten compounds were identified, hydroxytyrosol, verbascoside derivate and hydroxytyrosol glycol being the most abundant. Total phenolic content varied between 2.37 and 64.17 ?g mg(-1) of extract. The IC50 values from the antioxidant activity methods tested varied between 0.30 and 1.66 mg mL(-1) for reducing power, and between 0.13 and 0.83 mg mL(-1) for DPPH. The results obtained in the antioxidant activity were extremely significantly correlated with the main phenolic compounds as well as with the total phenolic content. A principal component analysis allowed grouping the samples according to their phenolic composition and antioxidant potential. Table olive extracts were able to inhibit some pathogenic microorganisms, mainly Gram-positive bacteria. Higher antimicrobial inhibition was recorded in the extracts rich in phenolic compounds and higher antioxidant potential. PMID:25266980

Malheiro, Ricardo; Mendes, Patrícia; Fernandes, Fátima; Rodrigues, Nuno; Bento, Albino; Pereira, José Alberto

2014-11-19

369

The nature of lithium battery materials under oxygen evolution reaction conditions.  

PubMed

Transition-metal oxide and phosphate materials, commonly used for lithium battery devices, are active as oxygen evolution reaction (OER) catalysts under alkaline and neutral solution conditions. Electrodes composed of LiCoO(2) and LiCoPO(4) exhibit progressive deactivation and activation for OER catalysis, respectively, upon potential cycling at neutral pH. The deactivation of LiCoO(2) and activation of LiCoPO(4) are coincident with changes in surface morphology and composition giving rise to spinel-like and amorphous surface structures, respectively. The amorphous surface structure of the activated LiCoPO(4) is compositionally similar to that obtained from the electrodeposition of cobalt oxide materials from phosphate-buffered electrolyte solutions. These results highlight the importance of a combined structural and electrochemical analysis of the materials surface when assessing the true nature of the OER catalyst. PMID:23033962

Lee, Seung Woo; Carlton, Christopher; Risch, Marcel; Surendranath, Yogesh; Chen, Shuo; Furutsuki, Sho; Yamada, Atsuo; Nocera, Daniel G; Shao-Horn, Yang

2012-10-17

370

Natural radioactivity of Indian building materials and by-products.  

PubMed

Conventional building materials and by-products from coal power plants which are being used or have the potential for use in buildings in India were analysed for natural radioactivity due to the presence of 226Ra, 232Th and 40K using gamma-ray spectroscopy. The materials examined in this work showed the radioactivity levels below the limit estimated from radium equivalent activity the criterion formula for gamma-activity suggested for acceptable radiation doses attributable to building materials in OECD countries. PMID:10376322

Kumar, V; Ramachandran, T V; Prasad, R

1999-07-01

371

Determination of Residual Stress in Composite Materials Using Ultrasonic Waves  

NASA Technical Reports Server (NTRS)

The performance of high temperature composites can be significantly affected by the presence of residual stresses. These stresses arise during cooling processes from fabrication to room temperature due to mismatch of thermal expansion coefficients between matrix and fiber materials. This effect is especially pronounced in metal matrix and intermetallic composites. It can lead to plastic deformations, matrix cracking and fiber/matrix interface debonding. In this work the feasibility of ultrasonic techniques for residual stress assessment in composites is addressed. A novel technique for absolute stress determination in orthotropic materials from angular dependencies of ultrasonic velocities is described. The technique is applicable for determination of both applied and residual stresses and does not require calibration measurements on a reference sample. The important advantage of this method is that stress is determined simultaneously with stress-dependent elastic constants and is thus decoupled from the material texture. It is demonstrated that when the principal plane stress directions coincide with acoustical axes, the angular velocity data in the plane perpendicular to the stress plane may be used to determine both stress components. When the stress is off the acoustical axes, the shear and the difference of the normal stress components may be determined from the angular dependence of group velocities in the plane of stresses. Synthetic sets of experimental data corresponding to materials with different anisotropy and stress levels are used to check the applicability of the technique. The method is also verified experimentally. A high precision ultrasonic wave transmission technique is developed to measure angular dependence of ultrasonic velocities. Examples of stress determination from experimental velocity data are given. A method is presented for determination of velocities of ultrasonic waves propagating through the composite material with residual stresses. It is based on the generalized self-consistent multiple scattering model. Calculation results for longitudinal and shear ultrasonic wave velocities propagating perpendicular to the fibers direction in SCS-6/Ti composite with and without residual stresses are presented. They show that velocity changes due to presence of stresses are of order 1%.

Rokhlin, S. I.

1997-01-01

372

Theoretical prediction of dynamic composite material properties for hypervelocity impact simulations  

Microsoft Academic Search

Recent advances in the description of fibre-reinforced polymer composite material behaviour under extreme loading rates provide a significant extension in capabilities for numerical simulation of hypervelocity impact on composite satellite structures. Given the complexity of the material model, extensive material characterisation is required, however, as the properties of composite materials are commonly tailored for a specific application, experimental characterisation is

S. Ryan; M. Wicklein; A. Mouritz; W. Riedel; F. Schäfer; K. Thoma

2009-01-01

373

Modeling Natural Space Ionizing Radiation Effects on External Materials  

NASA Technical Reports Server (NTRS)

Predicting the effective life of materials for space applications has become increasingly critical with the drive to reduce mission cost. Programs have considered many solutions to reduce launch costs including novel, low mass materials and thin thermal blankets to reduce spacecraft mass. Determining the long-term survivability of these materials before launch is critical for mission success. This presentation will describe an analysis performed on the outer layer of the passive thermal control blanket of the Hubble Space Telescope. This layer had degraded for unknown reasons during the mission, however ionizing radiation (IR) induced embrittlement was suspected. A methodology was developed which allowed direct comparison between the energy deposition of the natural environment and that of the laboratory generated environment. Commercial codes were used to predict the natural space IR environment model energy deposition in the material from both natural and laboratory IR sources, and design the most efficient test. Results were optimized for total and local energy deposition with an iterative spreadsheet. This method has been used successfully for several laboratory tests at the Marshall Space Flight Center. The study showed that the natural space IR environment, by itself, did not cause the premature degradation observed in the thermal blanket.

Alstatt, Richard L.; Edwards, David L.; Parker, Nelson C. (Technical Monitor)

2000-01-01

374

TRANSTRAIN: A program to compute strain transformations in composite materials  

SciTech Connect

Over the years, the solid rocket motor community has made increasing use of composite materials for thermal and structural applications. This is particularly true of solid rocket nozzles, which have used carbon phenolic and, increasingly, carbon-carbon materials to provide structural integrity and thermal protection at the high temperatures encountered during motor burn. To evaluate the degree of structural performance of nozzles and their materials and to verify analysis models, many subscale and full-scale tests are run. These provide engineers with valuable data needed to optimize design and to analyze nozzle hardware. Included among these data are strains, pressures, thrust, temperatures, and displacements. Recent nozzle test hardware has made increasing use of strain gauges embedded in the carbon composite material to measure internal strains. In order to evaluate strength, these data must be transformed into strains along the fiber directions. The fiber-direction stresses can then be calculated. A computer program written to help engineers correctly manipulate the strain data into a form that can be used to evaluate structural integrity of the nozzle is examined.

Ahmed, R.

1990-07-01

375

Development of active composites using conventional structural materials  

NASA Astrophysics Data System (ADS)

Development of new active composites using conventional structural materials are described in this paper. An active CFRP/Al laminate was proposed and developed, which became flat when it was kept at its hot pressing temperature 393K by electric resistance heating of the carbon fiber in the CFRP layer, and its curvature increased when it was air-cooled. The mechanism of its actuation is fundamentally the same as that of bimetal, but its major advantage is its directional actuation due to directionality of the reinforcement fiber and its anisotropy of CTE. FRM based active material was also developed. SiC fiber reinforced aluminum composite was laminated with unreinforced aluminum plate by the interphase forming/bonding method using copper insert foil. Curvature of the material monotonically changed as a function of temperature. It was also clarified that the copper concentrated around the SiC fiber which was introduced by the interphase forming/bonding method contributed to curvature increase of the actuator. In order to detect its deformation, pre-notched optical fiber was embedded in the active material and successfully broken in it to form an optical loss type sensor. Using this sensor, a simple relation between curvature change and change of optical loss to be used for its shape control was successfully obtained.

Asanuma, Hiroshi; Haga, Osamu; Hakoda, Genji; Ohira, Junichiro

2001-04-01

376

Fatigue Crack Measurement in Composite Materials by Ultrasonic Methods  

NASA Technical Reports Server (NTRS)

The nondestructive detection of intra-ply microcracking in unlined pressure vessels fabricated from composite materials is critical to ensuring mission success. Microcracking in composite structures due to combined fatigue and cryogenic thermal loading can be very troublesome to detect in-service and when it begins to link through the thickness can cause leakage and failure of the structure. These leaks may lead to loss of pressure/propellant, increased risk of explosion and possible cryo-pumping. The work presented herein develops a method and an instrument to locate and measure intraply fatigue cracking through the thickness of laminated composite material by means of correlation with ultrasonic resonance. Resonant ultrasound spectroscopy provides measurements which are, sensitive to both the microscopic and macroscopic properties of an object. Elastic moduli, acoustic attenuation, and geometry can all be probed. The approach is based on the premise of half-wavelength resonance. The method injects a broadband ultrasonic wave into the test structure using a swept frequency technique. This method provides dramatically increased energy input into the test article, as compared to conventional spike pulsed ultrasonics. This relative energy increase improves the ability to measure finer details in the materials character, such as micro-cracking and porosity. As the micro-crack density increases, more interactions occur with the higher frequency (small wavelength) components of the signal train causing the spectrum to shift toward lower frequencies. Preliminary experiments have verified a measurable effect on the resonance spectrum of the ultrasonic data to detect microcracking. Methods involving self organizing neural networks and other clustering algorithms show that the resonance ultrasound signatures from composites vary with the degree of microcracking and can be separated and identified.

Walker, James L.; Russell, Samuel S.; Suits, Michael W.; Workman, Gary L.; Watson, Jason M.; Thom, Robert (Technical Monitor)

2002-01-01

377

Influence of Material Distribution on Impact Resistance of Hybrid Composites  

NASA Technical Reports Server (NTRS)

Impact events occur in a wide variety of circumstances. A typical example is a bullet impacting a target made of composite material. These impact events produce time-varying loads on a structure that can result in damage. As a first step to understanding the damage resistance issue in composite laminates, an accurate prediction of the transient response during an impact event is necessary. The analysis of dynamic loadings on laminated composite plates has undergone considerable development recently. Rayleigh-Ritz energy method was used to determine the impact response of laminated plates. The impact response of composite plates using shear deformation plate theory was analyzed. In recent work a closed-form solution was obtained for a rectangular plate with four edges simply supported subjected to a center impact load using classical plate theory. The problem was further investigated and the analysis results compared of both classical plate theory and shear deformation theory, and found that classical plate theory predicts very accurate results for the range of small deformations considered. In this study, the influence of cross sectional material distribution on the comparative impact responses of hybrid metal laminates subjected to low and medium velocity impacts is investigated. A simple linear model to evaluate the magnitude of the impact load is proposed first, and it establishes a relation between the impact velocity and the impact force. Then a closed-form solution for impact problem is presented. The results were compared with the finite element analysis results. For an 11 layer-hybrid laminate, the impact response as a function of material distribution in cross-section is presented. With equal areal weight, the effect of the number of laminate layers on the impact resistance is also investigated. Finally, the significance of the presented results is discussed.

Abatan, Ayu; Hu, Hurang

1998-01-01

378

Semi-annual report on materials research in support of superconducting machinery. Final report. [Composite materials  

Microsoft Academic Search

The following five areas are discussed: advanced composites, elastic properties, fatigue resistance and fracture toughness, magnetothermal conductivity, and thermal conductivity. Material properties were studied over the temperature range 4 to 300°K. Materials studied include: aluminum alloy 5083, copper--0.3 cadmium--0.3 tin, copper--28 nickel, iron--48 nickel, 3.5 Ni and 9 Ni steels, titanium--4 aluminum--6 vanadium, titanium--5 aluminum--2.5 tin, stainless steel 21-6-9, several

R. P. Reed; J. G. Hust; M. B. Kasen; H. M. Ledbetter; H. I. McHenry

1976-01-01

379

Explorations in the application of nanotechnology to improve the mechanical properties of composite materials  

NASA Astrophysics Data System (ADS)

This thesis presents the research achievements on the design, preparation, characterization, and analysis of a series of composite materials. By studying the interface interaction of the composite materials using nanotechnology, we developed composite materials that achieve satisfactory mechanical properties in two classes of materials. Durable press (DP) natural textiles are important consumer products usually achieved by erosslinking the molecules in the textiles to achieve long-term wrinkle resistance, which, however, also leads to the simultaneous significant drop of mechanical properties. Herein, a series of polymeric nanoparticl es were investigated, the application of as little as ˜0.14 wt% addition of the nanoparticles improved the mechanical property of the DP cotton fabric by 56% in tearing resistance and 100% in abrasion resistance; the loss in recovery angle is negligible. The author also studied the enzyme-triggered DP treatments of silk fabrics, as a green process method. After the treatment of enzymes, excellent DP property was achieved with improved strain property. Injectable calcium phosphate powder containing acrylic bone cements are widely used in orthopedic surgery to fix artificial prostheses. However, the bending strength is still unsatisfactory. The author modified the surface of the strontium (Sr) containing hydroxyapatite (HA) filler powders with acrylolpamidronate in order to improve the overall mechanical performance of the bone cement composites. By adding 0.25 wt% of acrylolpamidronate to the Sr-HA nanopowders, more than 19% of the bending strength and more than 23% compression strength of the Sr-HA bone cement were improved. Biological evaluations revealed that these bone cement composites were biocompatible and bioactive in cell culture. The results obtained in this thesis work show an effective method to significantly enhance the mechanical properties of composite materials. Different from other available methods, by developing a new series of chemical compounds and nanoparticles, we successfully bound them to the surface or to the constitutional components of the materials through covalent bond. The treatment can enhance and modulate the interface-bonding of the filler materials and enhances the mechanical property of the surface through grafting a thin nano-layer. Since only surface reaction is involved, very small amount of the new material is needed, and the treatment can be readily integrated to the existing processes. The work is instructive in modifying available composite materials to acquire ultra-high mechanical performance.

Yang, Cheng

380

Voigt waves in electro-optic homogenized composite materials  

NASA Astrophysics Data System (ADS)

A study was undertaken into Voigt wave propagation in a homogenized composite material (HCM). The HCM investigated arose from a porous electro-optic host material infiltrated by a fluid of refractive index na, considered in the long-wavelength regime. The extended Bruggeman homogenization formalism was employed to estimate the constitutive parameters of the HCM. In principle, the directions which support Voigt wave propagation in the HCM may be controlled by means of an applied dc electric field; and the degree of control may be sensitive to the porosity of the host material, the shapes, sizes and orientations of the pores, as well as the refractive index na. Here the theoretical methodology is presented; numerical results are presented elsewhere.

Mackay, Tom G.

2014-08-01

381

Composition and mineralogy of dark material units on Vesta  

NASA Astrophysics Data System (ADS)

Vesta is the asteroid with the largest albedo variation among the known rocky Solar System objects and shows a widespread occurrence of dark material (DM) and bright material (BM) units. In the first observation phases by the Dawn spacecraft, two main extensions of low albedo areas were identified on Vesta and found to be closely correlated with carbonaceous, OH-rich, material. In this work we use the hyperspectral data provided by the VIR-Dawn imaging spectrometer onboard Dawn to detect and analyze individual, well-defined, dark material units. We define DM units assuming a relative criterion, i.e. reflectance lower than the surroundings. By coupling visible and infrared images of the same area we are able to select real dark material units, discarding false detections created by shadowing effects. A detailed final catalogue of 123 dark units is presented, containing the geographical parameters and the main spectral characteristics for each unit. Independently of the geological context of the dark units, all DMs show similar spectral properties, dominated by the pyroxene absorption features, as is the average spectrum of Vesta. This finding suggests a similar composition, with the presence of darkening agents that also weaken pyroxene band depths. The majority (90%) of the DM units shows a positive correlation between low albedo and an OH band centered at 2.8 ?m, confirming the hypothesis that the darkening agents are carbonaceous chondrites, probably delivered by low-velocity impacts of primitive asteroids. A comparison with laboratory spectra allows us to better constrain the size and the composition of the darkening agents. These DM areas seem to be made of eucritic material. The regolith grain size seems to be nearly constant around an average value of 25 ?m, and is quite homogenous at least in the first hundreds of meters beneath the Vesta surface, suggesting similar processing mechanisms for both DM and BM.

Palomba, Ernesto; Longobardo, Andrea; De Sanctis, Maria Cristina; Zambon, Francesca; Tosi, Federico; Ammannito, Eleonora; Capaccioni, Fabrizio; Frigeri, Alessandro; Capria, Maria Teresa; Cloutis, Edward A.; Jaumann, Ralf; Combe, Jean-Philippe; Raymond, Carol A.; Russell, Christopher T.

2014-09-01

382

Woven fabric composite material model with material nonlinearity for nonlinear finite element simulation  

Microsoft Academic Search

The objective of the current investigation is to develop a simple, yet generalized, model which considers the two-dimensional extent of woven fabric, and to have an interface with nonlinear finite element codes. A micromechanical composite material model for woven fabric with nonlinear stress-strain relations is developed and implemented in ABAQUS for nonlinear finite element structural analysis. Within the model a

A. Tabiei; Y. Jiang

1999-01-01

383

Composition of Surface Materials on the Moons of Mars  

NASA Astrophysics Data System (ADS)

The two small asteroid-like bodies orbiting Mars, Phobos and Deimos, are low albedo and exhibit similar visible to near-infrared spectra. Determining the origin of these moons is closely tied to determining their composition. From available spectroscopic data Phobos exhibits two distinct types of materials across its surface, and data from both Mars Express and Mars Reconnaissance Orbiter have provided additional details about the properties of these materials and their spatial relation to one another. Although no prominent diagnostic absorptions have been detected, systematic weak features are seen in some data. An extensive regolith is observed to have developed on both moons with characteristics that may be unique due to their special environment in Mars orbit. Understanding the character and evolution of the regolith of Phobos and Deimos is central to interpreting the moons' physical and optical properties. The cumulative data available for compositional analyses across the surface of Phobos and Deimos, however, remain incomplete in scope and character and ambiguous in interpretation. Consequently the composition of the moons of Mars remains uncertain.

Pieters, Carle M.; Murchie, Scott; Thomas, Nicolas; Britt, Daniel

2014-11-01

384

Finite Element Modeling of Transient Thermography Inspection of Composite Materials  

NASA Technical Reports Server (NTRS)

Several finite element models of defects such as debond and void have been developed for composite panels subjected to transient thermography inspection. Since the exact nature of the heat generated from the flash lamps is unknown, direct comparison between FEA and experimental results is not possible. However, some similarity of the results has been observed. The shape of the time curve that simulates the heat flux from the flash lamps has minimal effect on the temperature profiles. Double the number of flash lamps could increase the contrast of thermal image and define the shape of defect better.

Chu, Tsuchin Philip

1998-01-01

385

A boundary element analysis of metal matrix composite materials  

SciTech Connect

Various Metal Matrix Composite systems are modeled using Boundary Element Methods. The predicted material properties are compared with properties obtained using Finite Element Methods, and good agreement is found. When elastic properties are sought, BEM has a distinct advantage over FEM in terms of efficiency. When plastic properties are simulated the advantage is of a lesser magnitude. BEM also allows easy modeling of the behavior of the composite at the interface between the strengthening particle and the matrix. Such a model is implemented here. Finally, the predicted elastic properties of MMC systems of various reinforcement content are compared with experimentally determined properties of corresponding specimens. Good agreement is found for reinforcement volume fractions up to 20%.

Mammoli, A.A.; Bush, M. [Univ. of Western Australia, Nedlands (Australia). Dept. of Mechanical and Materials Engineering

1993-12-31

386

Recycling By Solvolysis Thermosetting Composite Materials Of Sustainable Surface Transport  

SciTech Connect

A solvolysis process is studied to degrade an unsaturated polyester resin based on DCPD (dicyclopentadiene) and crosslinked with styrene, as the matrix of a composite material reinforced with long glass fibers. The study presented here investigates in particular the hydrolysis in conditions below the critical point of water (T<374 deg. C and P<221bar) in a batch reactor. Process window and parameter influences were studied by a Design of Experiments (DOE) approach (1). A tar-like substance issued from thermal degradations is formed in greater or lesser quantities depending on the operating conditions, and coats the fibers. The appearance of the composite samples and the degree of conversion for the degradation at 250 deg. C lead us to make a parallel with osmosis phenomena to explain the initiation mechanism of the degradation.

Oliveux, Geraldine; Le Gal La Salle, Eric [Laboratoire de Thermocinetique de Nantes (LTN), UMR CNRS 6607, Ecole Polytechnique de l'Universite de Nantes, Rue Christian Pauc, 44303 Nantes (France); Bailleul, Jean-Luc [Laboratoire Energetique, Mecanique et Materiaux(LE2M) de l'Institut Catholique des Arts et Metiers de Nantes, 35 avenue du champ de Manoeuvres, 44470 Carquefou (France)

2011-01-17

387

Early detection of fatigue damage in composite materials  

NASA Technical Reports Server (NTRS)

Early detection of fatigue damage in composite materials by nondestructive inspection (NDI) techniques has been demonstrated for glass/epoxy, graphite/glass/epoxy, and graphite/epoxy composites. Modulus and temperature were monitored and a correlation between them observed. Axial modulus and torsional modulus changes were a function of the laminate orientation. Torsional modulus measurements and coin tap tests were performed at 0, 1 million, 5 million, and 10 million cycles, on axial fatigue specimens. Three distinct regions were noted. In the primary region a small but rapid change in stiffness was noted in the first few thousand cycles. This was followed by a secondary region of little or no stiffness change. The tertiary region was characterized by an increasing rate of stiffness change leading to fracture. NDI procedures including holographic interferometry, ultrasonics, penetrant, and X-ray radiography were evaluated for fatigue damage detection.

Salkind, M. J.

1975-01-01

388

Damage and strength of composite materials: Trends, predictions, and challenges  

NASA Technical Reports Server (NTRS)

Research on damage mechanisms and ultimate strength of composite materials relevant to scaling issues will be addressed in this viewgraph presentation. The use of fracture mechanics and Weibull statistics to predict scaling effects for the onset of isolated damage mechanisms will be highlighted. The ability of simple fracture mechanics models to predict trends that are useful in parametric or preliminary designs studies will be reviewed. The limitations of these simple models for complex loading conditions will also be noted. The difficulty in developing generic criteria for the growth of these mechanisms needed in progressive damage models to predict strength will be addressed. A specific example for a problem where failure is a direct consequence of progressive delamination will be explored. A damage threshold/fail-safety concept for addressing composite damage tolerance will be discussed.

Obrien, T. Kevin

1994-01-01

389

Compressive strength of fiber-reinforced composite materials  

NASA Technical Reports Server (NTRS)

Results of an experimental and analytical investigation of the compressive strength of unidirectional boron-epoxy composite material are presented. Observation of fiber coordinates in a boron-epoxy composite indicates that the fibers contain initial curvature. Combined axial compression and torsion tests were conducted on boron-epoxy tubes and it was shown that the shear modulus is a function of axial compressive stress. An analytical model which includes initial curvature in the fibers and permits an estimate of the effect of curvature on compressive strength is proposed. Two modes of failure which may result from the application of axial compressive stress are analyzed - delamination and shear instability. Based on tests and analysis, failure of boron-epoxy under axial compressive load is due to shear instability.

Davis, J. G., Jr.

1975-01-01

390

Tuneable broadband optical filter based on soft-composite materials  

NASA Astrophysics Data System (ADS)

We report on the realization and characterization of a ‘free space’ diffractive optical filter based on a periodic structure realized in soft composite materials. By combining a high stability optical holographic setup with a light sensitive composite mixture, we have realized a structure made of polymeric slices alternated to pure, well aligned, nematic liquid crystals. Its polarization dependent diffractive properties have been exploited for realizing a diffractive, band-gap based, broadband optical filter. The sample is characterized in terms of its morphological, optical and electro-optical properties. We show that both electric fields and temperature variations can be exploited to tune the position of the diffractive band-gap of about 83 nm and 116 nm respectively.

De Sio, Luciano; Caligiuri, Vincenzo; Umeton, Cesare

2014-06-01

391

Recycling By Solvolysis Thermosetting Composite Materials Of Sustainable Surface Transport  

NASA Astrophysics Data System (ADS)

A solvolysis process is studied to degrade an unsaturated polyester resin based on DCPD (dicyclopentadiene) and crosslinked with styrene, as the matrix of a composite material reinforced with long glass fibers. The study presented here investigates in particular the hydrolysis in conditions below the critical point of water (T<374° C and P<221bar) in a batch reactor. Process window and parameter influences were studied by a Design of Experiments (DOE) approach (1). A tar-like substance issued from thermal degradations is formed in greater or lesser quantities depending on the operating conditions, and coats the fibers. The appearance of the composite samples and the degree of conversion for the degradation at 250° C lead us to make a parallel with osmosis phenomena to explain the initiation mechanism of the degradation.

Oliveux, Géraldine; Le Gal La Salle, Eric; Bailleul, Jean-Luc

2011-01-01

392

Physics in ``Polymers, Composites, and Sports Materials" an Interdisciplinary Course  

NASA Astrophysics Data System (ADS)

The undergraduate science course described uses the themes of polymers and composites, as used in sports materials, to teach some key concepts in introductory chemistry and physics. The course is geared towards students who are interested in science, but are still completing prerequisite mathematics courses required for science majors. Each class is built around a laboratory activity. Atoms, molecules and chemical reactions are taught in reference to making polyvinyl acetate (white glue) and polyvinyl alcohol (gel glue). These materials, combined with borax, form balls which are subsequently used in physics activities centered on free-fall and the coefficient of restitution. These activities allow the introduction of kinematics and dynamics. A free fall activity involving ice pellets, with and without embedded tissue paper, illustrates the properties of composites. The final series of activities uses balls, shoes, racquets and bats to further illustrate dynamics concepts (including friction, momentum and energy). The physical properties of these sports objects are discussed in terms of the materials of which they are made. The evaluation plan to determine the effectiveness of these activities and preliminary results are also presented.

Hagedorn, Eric; Suskavcevic, Milijana

2007-10-01

393

Finite element analysis of composites materials for aerospace applications  

NASA Astrophysics Data System (ADS)

Composites materials are intended to be used more extensively as an alternative of aluminum structure in aircraft and aerospace applications. This is due to their attractive properties as high strength-to-weight ratio and stiffness-to-weight ratio. Besides that it clarifies the growing interest for composites materials due to advantages of lightweight, high strength, high stiffness, superior fatigue life, tremendous corrosion resistance and low cost manufacturing. In this study, a finite element analysis (FEA) of fiberglass unidirectional E-type was analyzed in the framework of ABAQUS finite element commercial software. The analysis was done to quantify the mechanical properties and response of unidirectional E-glass in term of tensile, compression and thermal responses. From the analysis, the maximum and minimum values of stress and strain for E-glass 21xK43 Gevetex and Silenka E-glass 1200tex were obtained and stress-strain curve is presented. The ultimate load of failure, elastic behavior, tensile strength and other properties for each laminated plates under tensile and thermal-stress are determined from stress-strain curves. The simulation will run twice for each material where the first simulation based on orientation angles of 45° for ply-1, -45° for ply-2 and 90° for ply-3 while the second simulation, the orientation angles is 0° for all plies. The simulation is successfully conducted and verified by experimental data.

Nurhaniza, M.; Ariffin, M. K. A.; Ali, Aidy; Mustapha, F.; Noraini, A. W.

2010-05-01

394

Interlaminar shear fracture toughness and fatigue thresholds for composite materials  

NASA Technical Reports Server (NTRS)

Static and cyclic end notched flexure tests were conducted on a graphite epoxy, a glass epoxy, and graphite thermoplastic to determine their interlaminar shear fracture toughness and fatigue thresholds for delamination in terms of limiting values of the mode II strain energy release rate, G-II, for delamination growth. The influence of precracking and data reduction schemes are discussed. Finite element analysis indicated that the beam theory calculation for G-II with the transverse shear contribution included was reasonably accurate over the entire range of crack lengths. Cyclic loading significantly reduced the critical G-II for delamination. A threshold value of the maximum cyclic G-II below which no delamination occurred after one million cycles was identified for each material. Also, residual static toughness tests were conducted on glass epoxy specimens that had undergone one million cycles without delamination. A linear mixed-mode delamination criteria was used to characterize the static toughness of several composite materials; however, a total G threshold criterion appears to characterize the fatigue delamination durability of composite materials with a wide range of static toughness.

O'Brien, T. Kevin; Murri, Gretchen B.; Salpekar, Satish A.

1989-01-01

395

Interlaminar shear fracture toughness and fatigue thresholds for composite materials  

NASA Technical Reports Server (NTRS)

Static and cyclic end notched flexure tests were conducted on a graphite epoxy, a glass epoxy, and graphite thermoplastic to determine their interlaminar shear fracture toughness and fatigue thresholds for delamination in terms of limiting values of the mode II strain energy release rate, G-II, for delamination growth. The influence of precracking and data reduction schemes are discussed. Finite element analysis indicated that the beam theory calculation for G-II with the transverse shear contribution included was reasonably accurate over the entire range of crack lengths. Cyclic loading significantly reduced the critical G-II for delamination. A threshold value of the maximum cyclic G-II below which no delamination occurred after one million cycles was identified for each material. Also, residual static toughness tests were conducted on glass epoxy specimens that had undergone one million cycles without delamination. A linear mixed-mode delamination criteria was used to characterize the static toughness of several composite materials; however, a total G threshold criterion appears to characterize the fatigue delamination durability of composite materials with a wide range of static toughness.

Obrien, T. Kevin; Murri, Gretchen B.; Salpekar, Satish A.

1987-01-01

396

Naturally Occurring Radioactive Materials in Cargo at US Borders  

SciTech Connect

In the U.S. and other countries, large numbers of vehicles pass through border crossings each day. The illicit movement of radioactive sources is a concern that has resulted in the installation of radiation detection and identification instruments at border crossing points. This activity is judged to be necessary because of the possibility of an act of terrorism involving a radioactive source that may include any number of dangerous radionuclides. The problem of detecting, identifying, and interdicting illicit radioactive sources is complicated by the fact that many materials present in cargo are somewhat radioactive. Some cargo contains naturally occurring radioactive material or technologically-enhanced naturally occurring radioactive material that may trigger radiation portal monitor alarms. Man-made radioactive sources, especially medical isotopes, are also frequently observed and produce alarms. Such nuisance alarms can be an operational limiting factor for screening of cargo at border crossings. Information about the nature of the radioactive materials in cargo that can interfere with the detection of radionuclides of concern is necessary. This paper provides such information for North American cargo, but the information may also be of use to border control officials in other countries. (PIET-43741-TM-361)

Kouzes, Richard T.; Ely, James H.; Evans, John C.; Hensley, Walter K.; Lepel, Elwood A.; McDonald, Joseph C.; Schweppe, John E.; Siciliano, Edward R.; Strom, Daniel J.; Woodring, Mitchell L.

2006-01-01

397

Analysis and chemical composition of larnite-rich ultrarefractory materials  

Microsoft Academic Search

Larnite (b-Ca2SiO4) is a rare, little known compound. However, despite its scarcity, larnite is found in different natural settings, almost always under thermodynamic conditions of around 0.2–1kbar and 1000–1100°C. Larnite can also be formed artificially, especially during the synthesis of high technology refractory and ceramic materials, and as a mineral component of some industrial slags and portland cements. This work

J Mart??nez-Fr??as; R. Benito; G. Wilson; A. Delgado; T. Boyde; K Marti

2004-01-01

398

Overview of naturally occurring Earth materials and human health concerns  

NASA Astrophysics Data System (ADS)

The biosphere and the Earth's critical zone have maintained a dynamic equilibrium for more than 3.5 billion years. Except for solar energy, almost all terrestrial substances necessary for life have been derived from near-surface portions of the land, hydrosphere, and atmosphere. If aggregate biological activities are less than the rate of nutrient supply and/or resource renewal, sustained population growth is possible. Where the replenishment rate of a life-sustaining Earth material is finite, usage may reach a condition of dynamic equilibrium in which biological consumption equals but on average cannot exceed the overall supply. Although large, most natural resources are present in finite abundances; for such commodities, excessive present-day human utilization reduces future availability, and thus the ultimate planetary carrying capacity for civilization. Intensive use of Earth materials has enhanced the quality of life, especially in the developed nations. Still, natural background levels, and Earth processes such as volcanic eruptions, as well as human activities involving agriculture, construction, and the extraction, refining, and transformation of mineral resources have led to harmful side effects involving environmental degradation and public health hazards. Among naturally and anthropogenically induced risks are bioaccessible airborne dusts and gases, soluble pollutants in agricultural, industrial, and residential waters, and toxic chemical species in foods and manufactured products. At appropriate levels of ingestion, many Earth materials are necessary for existence, but underdoses and overdoses have mild to serious consequences for human health and longevity. This overview briefly sketches several natural resource health hazards. Included are volcanic ash + aerosols + gases, mineral dusts, non-volcanic aerosols + nanoparticles, asbestos + fibrous zeolites, arsenic, fluorine, iodine, uranium + thorium + radium + radon + polonium, selenium, mercury, copper, lead, chromium, and cadmium. Also noted are health effects of natural disasters, and an obligatory future sustainable consumption of natural resources. Not treated are the overwhelming adverse effects of malnutrition, lack of potable water, inadequate sanitation, fossil fuel usage, mining, manufacturing, and agricultural pollution, or environmental pathogens, nor are the important impacts of complex mixtures of Earth materials considered. With rise of the worldwide information network, economic globalization, and the industrial thrust of Developing Nations, the achievement of natural resource sustainability has emerged as a strategic imperative. Accompanying increased rates of Earth materials consumption and attendant environmental change, substantially improved, universal public health will require a major global effort, integrating collaborations among geoscientists, medical researchers, and epidemiologists. Governments and NGOs must provide important support of such cooperative efforts, and both health and Earth scientists must cross disciplinary and national boundaries.

Ernst, W. G.

2012-10-01

399

ECCM15 -15TH EUROPEAN CONFERENCE ON COMPOSITE MATERIALS, Venice, Italy, 24-28 June 2012  

E-print Network

ECCM15 - 15TH EUROPEAN CONFERENCE ON COMPOSITE MATERIALS, Venice, Italy, 24-28 June 2012 1 VOID the viscous pressure. #12;ECCM15 - 15TH EUROPEAN CONFERENCE ON COMPOSITE MATERIALS, Venice, Italy, 24-28 June

Paris-Sud XI, Université de

400

Natural radioactivity in building materials used in Changzhi, China.  

PubMed

The natural radioactivity levels of the commonly used building materials collected from Changzhi, China was analysed using gamma-ray spectroscopy. The activity concentrations of (226)Ra, (232)Th and (40)K in the investigated building materials range from 14.6 to 131.2, from 9.9 to 138.8 and from 96.1 to 819.0 Bq kg(-1), respectively. The results were compared with the reported data of other countries and with the worldwide mean activity of soil. The external and internal hazard indices and gamma index were calculated to assess the radiation hazard to residents. The external hazard index of all building materials are less than unity, while the internal hazard and gamma indexes of hollow brick and gravel aggregate exceed unity. The study shows that the investigated hollow brick and gravel aggregate are not suitable for use as building materials in dwellings. PMID:23407886

Yang, Guang; Lu, Xinwei; Zhao, Caifeng; Li, Nan

2013-08-01

401

Compressive strength after blast of sandwich composite materials.  

PubMed

Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene-acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3?m sized panels were subjected to blast of a Hopkinson-Cranz scaled distance of 3.02?m?kg(-1/3), 100?kg TNT equivalent at a stand-off distance of 14?m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411-413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast. PMID:24711494

Arora, H; Kelly, M; Worley, A; Del Linz, P; Fergusson, A; Hooper, P A; Dear, J P

2014-05-13

402

Effect of natural organic materials on cadmium and neptunium sorption  

SciTech Connect

In a batch sorption study of the effect of naturally occurring organic materials on the sorption of cadmium and neptunium on oxides and tuff surfaces, the model sorbents were synthetic goethite, boehmite, amorphous silicon oxides, and a crushed tuff material from Yucca Mountain, Nevada. An amino acid, 3-(3,4-dihydroxypheny)-DL-alanine (DOPA), and an aquatic-originated fulvic material, Nordic aquatic fulvic acid (NAFA), were used as model organic chemicals. Sorption isotherm results showed that DOPA sorption followed the order aluminum oxide > iron oxide > silicon oxide and that the amount of DOAP sorption for a given sorbent increased as the solution pH was raised. The sorption of cadmium and neptunium on the iron oxide was about ten times higher than that on the aluminum oxide. The sorption of cadmium and neptunium on natural tuff material was much lower than that on aluminum and iron oxides. The sorption of cadmium on iron and aluminum oxides was found to be influenced by the presence of DOPA, and increasing the amount of DOPA coating resulted in higher cadmium sorption on aluminum oxide. However, for iron oxide, cadmium sorption decreased with increasing DOPA concentration. The presence of the model organic materials DOPA and NAFA did not affect the sorption of neptunium on tuff material or on the iron and aluminum oxides. Spectroscopic results indicate that cadmium complexes strongly with DOPA. Therefore, the effect of the organic material, DOPA, on the cadmium sorption is readily observed. However, neptunium is possibly complexed weakly with organic material. Thus, DOPA and NAFA have little effect on neptunium sorption on all sorbents selected for study.

Kung, K.S.; Triay, I.R.

1994-10-01

403

Characterization of selected LDEF polymer matrix resin composite materials  

NASA Technical Reports Server (NTRS)

The characterization of selected graphite fiber reinforced epoxy (934 and 5208) and polysulfone (P1700) matrix resin composite materials which received 5 years and 10 months of exposure to the LEO environment on the Long Duration Exposure Facility is reported. Resin loss and a decrease in mechanical performance as well as dramatic visual effects were observed. However, chemical characterization including infrared, thermal, and selected solution property measurements showed that the molecular structure of the polymeric matrix had not changed significantly in response to this exposure. The potential effect of a silicon-containing molecular contamination of these specimens is addressed.

Young, Philip R.; Slemp, Wayne S.; Witte, William G., Jr.; Shen, James Y.

1991-01-01

404

Collagen hydrolysate based collagen/hydroxyapatite composite materials  

NASA Astrophysics Data System (ADS)

The aim of this study was to study the influence of collagen hydrolysate (HAS) on the formation of ternary collagen-hydrolysate/hydroxyapatite composite materials (COLL-HAS/HA). During the precipitation process of HA, a large amount of brushite is resulted at pH = 7 but, practically pure HA is obtained at pH ? 8. The FTIR data reveal the duplication of the most important collagen absorption bands due to the presence of the collagen hydrolysate. The presence of collagen hydrolysate is beneficial for the management of bone and joint disorders such as osteoarthritis and osteoporosis.

Ficai, Anton; Albu, Madalina Georgiana; Birsan, Mihaela; Sonmez, Maria; Ficai, Denisa; Trandafir, Viorica; Andronescu, Ecaterina

2013-04-01

405

Pressure-reaction synthesis of titanium composite materials  

DOEpatents

A pressure-reaction synthesis process for producing increased stiffness and improved strength-to-weight ratio titanium metal matrix composite materials comprising exothermically reacting a titanium powder or titanium powder alloys with non-metal powders or gas selected from the group consisting of C, B, N, BN, B.sub.4 C, SiC and Si.sub.3 N.sub.4 at temperatures from about 900.degree. to about 1300.degree. C., for about 5 to about 30 minutes in a forming die under pressures of from about 1000 to 5000 psi.

Oden, Laurance L. (Albany, OR); Ochs, Thomas L. (Albany, OR); Turner, Paul C. (Albany, OR)

1993-01-01

406

Characterization and performance of a self-healing composite material  

NASA Astrophysics Data System (ADS)

The development of a self-healing polymer-matrix composite material that possesses the ability to heal cracks autonomically is described. The system uses a monomer repair agent, dicyclopentadiene (DCPD), which is stored in an epoxy matrix by dispersing microcapsules containing the liquid repair agent throughout the matrix. When the material is damaged, cracks propagate through the material and break open the microcapsules, releasing the repair agent into the crack plane. Finally, the DCPD repair agent solidifies by ring-opening metathesis polymerization (ROMP) after coming in contact with a ruthenium-based catalyst (Grubbs' catalyst) dispersed in the matrix. The process by which the DCPD-filled microcapsules are prepared and the various techniques to characterize the microcapsules are discussed. The cure kinetics of poly dicyclopentadiene (pDCPD) prepared by ROMP with three different concentrations of Grubbs' catalyst are examined using differential scanning calorimetry (DSC). The experimental data are used to test several different phenomenological kinetic models. The data are best modeled with a "model-free" isoconversional method. This analysis reveals that the activation energy increases significantly for degree of cure greater than 60%. Catalyst concentration is shown to have a large effect on the cure kinetics. Differential scanning calorimetry measurements on the catalyzed healing agent are also used to study the stability of the system to environmental conditions. A study of the healing of delamination damage in woven reinforced epoxy composites is performed. Three types of healing process are studied. In the first, a catalyzed monomer is manually injected into the delamination. In the second, a self-activated material is created by embedding the catalyst directly into the matrix of the composite, then manually injecting the monomer. In the third, a fully integrated in situ system is described with embedded microcapsules and catalyst. Double-cantilever-beam (DCB) and width-tapered double-cantilever-beam (WTDCB) specimens were tested to study the healing of delamination in composites by comparing the toughness of the virgin specimen with the toughness of the same specimen after healing was complete. Scanning electron microscopy is used to analyze the fracture surfaces and provide physical evidence of repair.

Kessler, Michael Richard

407

High-toughness graphite/epoxy composite material experiment  

NASA Technical Reports Server (NTRS)

This experiment was designed to measure the effect of near-earth space exposure on three mechanical properties of specially toughened 5208/T300 graphite/epoxy composite materials. The properties measured are elastic modulus, strength, and fracture toughness. Six toughness specimens and nine tensile specimens were mounted on an external frame during the 5.8-year orbit of the Long Duration Exposure Facility (LDEF). Three identical sets of specimens were manufactured at the outset: the flight set, a zero-time non-flight set, and a total-time non-flight set.

Felbeck, David K.

1993-01-01

408

Development of novel antibiofouling materials from natural phenol compounds  

NASA Astrophysics Data System (ADS)

Biofilms consist of a gelatinous matrix formed on a solid surface by microbial organisms.Biofilm is caused due to the adhesion of microbes to solid surfaces with production of extracellular polymers and the process of the biofilm formation is reffered to as biofouling.Biofouling causes serious problems in chemical, medical and pharmaceutical industries.Although there have been some antibiofouling materials developed over the years,no plausible results have been found yet.Natural polyphenolic compounds like flavanoids,cathechins have strong antioxidant and antimicrobial properties.Recently,apocynin,a phenol derivative,was polymerized to form oligomers,which can regulate intracellular pathways in cancer cells preventing cell proliferation and migration.These natural phenolic compounds have never been applied to solid surfaces to prevent biofouling.It is thought that probably because of the difficulty to crosslink them to form a stable coating.In this study,some novel polyphenolic compounds synthesized using enzymatic technique from cashew nut shell liquid,a cheap and renewable byproduct of the cashew industry are used as coating materials to prevent biofouling.The interaction of these materials with microbes preventing fouling on surfaces and the chemico-physical properties of the materials causing the antibiofouling effect will be discussed.It is critical to understand the antibiofouling mechanism of these materials for better design and application in various fields.

Chelikani, Rahul; Kim, Dong Shik

2007-03-01

409

Fluid Latent Heat Storage Materials Using Natural Substances  

NASA Astrophysics Data System (ADS)

A secondary refrigerant can be produced by using a multi-component material-such as a solution of some material in water, where there exists a liquid-solid co-existent region. Using this solid-liquid co-existent region, if we can form a two-phase solid-liquid flow, a high performance secondary refrigerant can be obtained. In addition, if the components of the multi-components material are existent in the nature, the secondary refrigerant can be used as a natural secondary refrigerant. In the present study, possibility of forming a new secondary refrigerant was investigated using a urea-water mixture. We made visual observations on crystal growth in a urea-water mixture, and using this information, we developed a new fluid latent heat storage material. And the differential scanning calorimeter (DSC) was used to investigate the phase diagram and the latent heat of a urea-water mixture. In addition, based on this phase diagram, the experiments were conducted under stirred conditions and fluid latent hest storage materials were investigated for various concentrations of urea-water mixtures.

Hokamura, Haku; Ohkubo, Hidetoshi

410

Multi scale analysis by acoustic emission of damage mechanisms in natural fibre woven fabrics/epoxy composites.  

NASA Astrophysics Data System (ADS)

This paper proposes to develop an experimental program to characterize the type and the development of damage in composite with complex microstructure. A multi-scale analysis by acoustic emission has been developed and applied to hemp fibre woven fabrics/epoxy composite. The experimental program consists of tensile tests performed on single yarn, neat epoxy resin and composite materials to identify their AE amplitude signatures. A statistical analysis of AE amplitude signals has been realised and correlated with microscopic observations. Results have enabled to identify three types of damage in composites and their associated AE amplitudes: matrix cracking, interfacial debonding and reinforcement damage and fracture. Tracking of these damage mechanisms in hemp/epoxy composites has been performed to show the process of damage development in natural fibre reinforced composites.

Bonnafous, C.; Touchard, F.; Chocinski-Arnault, L.

2010-06-01

411

Continuous microcellular foaming of polylactic acid/natural fiber composites  

NASA Astrophysics Data System (ADS)

Poly(lactic acid) (PLA), a biodegradable thermoplastic derived from renewable resources, stands out as a substitute to petroleum-based plastics. In spite of its excellent properties, commercial applications are limited because PLA is more expensive and more brittle than traditional petroleum-based resins. PLA can be blended with cellulosic fibers to reduce material cost. However, the lowered cost comes at the expense of flexibility and impact strength, which can be enhanced through the production of microcellular structures in the composite. Microcellular foaming uses inert gases (e.g., carbon dioxide) as physical blowing agents to make cellular structures with bubble sizes of less than 10 microm and cell-population densities (number of bubbles per unit volume) greater than 109 cells/cm³. These unique characteristics result in a significant increase in toughness and elongation at break (ductility) compared with unfoamed parts because the presence of small bubbles can blunt the crack-tips increasing the energy needed to propagate the crack. Microcellular foams have been produced through a two step batch process. First, large amounts of gas are dissolved in the solid plastic under high pressure (sorption process) to form a single-phase solution. Second, a thermodynamic instability (sudden drop in solubility) triggers cell nucleation and growth as the gas diffuses out of the plastic. Batch production of microcellular PLA has addressed some of the drawbacks of PLA. Unfortunately, the batch foaming process is not likely to be implemented in the industrial production of foams because it is not cost-effective. This study investigated the continuous microcellular foaming process of PLA and PLA/wood-fiber composites. The effects of the processing temperature and material compositions on the melt viscosity, pressure drop rate, and cell-population density were examined in order to understand the nucleation mechanisms in neat and filled PLA foams. The results indicated that the processing temperature had a strong effect of the rheology of the melt and cell morphology. Processing at a lower temperature significantly increased the cell nucleation rate of neat PLA (amorphous and semi-crystalline) because of the fact that a high melt viscosity induced a high pressure drop rate in the polymer/gas solution. The presence of nanoclay did not affect the homogeneous nucleation but increased the heterogeneous nucleation, allowing both nucleation mechanisms to occur during the foaming process. The effect of wood-flour (0-30 wt.%) and rheology modifier contents on the melt viscosity and cell morphology of microcellular foamed composites was investigated. The viscosity of the melt increased with wood-flour content and decreased with rheology modifier content, affecting the processing conditions (i.e., pressure drop and pressure drop rate) and foamability of the composites. Matching the viscosity of the composites with that of neat PLA resulted in the best cell morphologies. Physico-mechanical characterization of microcellular foamed PLA as a function of cell morphology was performed to establish process-morphology-property relationships. The processing variables, i.e., amount of gas injected, flow rate, and processing temperature affected the development of the cellular structure and mechanical properties of the foams.

Diaz-Acosta, Carlos A.

412

Parameterization of structures in HE composites using surrogate materials: A small angle neutron scattering investigation  

SciTech Connect

High explosive materials used in the nuclear stockpile are composites of crystalline high explosives (HE) with binder materials, such as Estane. In such materials, there are naturally occurring density fluctuations (defects) due to cracks, internal (in the HE) and external (in the binder) voids and other artifacts of preparation. Changes in such defects due to material aging can affect the response of explosives due to shock, impact and thermal loading. Modeling efforts are attempting to provide quantitative descriptions of explosive response from the lowest ignition thresholds to the development of full blown detonations and explosions, however, adequate descriptions of these processes require accurate measurements of a number of structural parameters of the HE composite. Since different defects are believed to affect explosive sensitivity in different ways it is necessary to quantitatively differentiate between defect types. The authors report here preliminary results of SANS measurements on surrogates for HE materials. The objective of these measurements was to develop methodologies using SANS techniques to parameterize internal void size distributions in a surrogate material, sugar, to simulate an HE used in the stockpile, HMX. Sugar is a natural choice as a surrogate material, as it has the same crystal structure, has similar intragranular voids and has similar mechanical properties as HMX. It is used extensively as a mock material for explosives. Samples were used with two void size distributions: one with a sufficiently small mean particle size that only small occluded voids are present in significant concentrations, and one where the void sizes could be larger. By using methods in small-angle neutron scattering, they were able to isolate the scattering arising from particle-liquid interfaces and internal voids.

Mang, J.T.; Hjelm, R.P.; Skidmore, C.B.; Howe, P.M.

1996-07-01

413

Inclusion of nanostructured materials in composite and double base propellants  

NASA Astrophysics Data System (ADS)

Two methods for including nanostructured reactive materials in composite and double base propellant systems were investigated. Initially, a multiscale computational model for determining the dispersion state of nanoparticles in various polymer bases was developed using molecular and dissipative particle dynamics. Systems of nanosize aluminum, boron, and copper (II) oxide were prepared in hydroxyl-terminated polybutadiene and examined using a variety of techniques to parameterize the model. The results of modeling and experiments showed that increasing nanoparticle concentrations tend to increase agglomerate size and quantity. In parallel, nanoscale reactive intermetallic-forming compounds were investigated as additives to increase propellant performance and burning rate. The nanoscale reactive material raised the burning rate temperature prefactor while simultaneously radically altering the agglomerate structure, providing tantalizing evidence for potential future performance gains.

Reese, David A.

414

Investigation of composite materials property requirements for sonic fatigue research  

NASA Technical Reports Server (NTRS)

Experimental techniques for determining the extensional and bending stiffness characteristics for symmetric laminates are presented. Vibrational test techniques for determining the dynamic modulus and material damping are also discussed. Partial extensional stiffness results intially indicate that the laminate theory used for predicting stiffness is accurate. It is clearly shown that the laminate theory can only be as accurate as the physical characteristics describing the lamina, which may vary significantly. It is recommended that all of the stiffness characteristics in both extension and bending be experimentally determined to fully verify the laminate theory. Dynamic modulus should be experimentally evaluated to determine if static data adequately predicts dynamic behavior. Material damping should also be ascertained because laminate damping is an order of magnitude greater than found in common metals and can significantly effect the displacement response of composite panels.

Patrick, H. V. L.

1985-01-01

415

Environmental exposure effects on composite materials for commercial aircraft  

NASA Technical Reports Server (NTRS)

The effects of environmental exposure on composite materials are determined. The environments considered are representative of those experienced by commercial jet aircraft. Initial results have been compiled for the following material systems: T300/5208, T300/5209, and T300/934. Future results will include AS-1/3501-6 and Kevlar 49/F161-188. Specimens are exposed on the exterior and interior of 737 airplanes of three airlines, and to continuous ground-level exposure at four locations. In addition, specimens are exposed in the laboratory to conditions such as: simulated ground-air-ground, weatherometer, and moisture. Residual strength results are presented for specimens exposed for up to five years at five ground-level exposure locations and on airplanes from one airline.

Coggeshall, R. L.

1985-01-01

416

Evaluation of hybrid composite materials in cylindrical specimen geometries  

NASA Technical Reports Server (NTRS)

Static and fatigue properties of three composite materials and hybrids were examined. The materials investigated were graphite/epoxy, S-glass/epoxy, PRD-49 (Kevlar 49)/epoxy, and hybrids in angle-ply configurations. A new type of edgeless cylindrical specimen was developed. It is a flattened tube with two flat sides connected by curved sections and it is handled much like the standard flat coupon. Special specimen fabrication, tabbing, and tab region reinforcing techniques were developed. Axial modulus, Poisson's ratio, strength, and ultimate strain were obtained under static loading from flattened tube specimens of nine laminate configurations. In the case of graphite/epoxy the tubular specimens appeared to yield somewhat higher strength and ultimate strain values than flat specimens. Tensile fatigue tests were conducted with all nine types of specimens and S-N curves obtained. Specimens surviving 10 million cycles of tensile loading were subsequently tested statically to failure to determine residual properties.

Liber, T.; Daniel, I. M.

1976-01-01

417

Selection of optimal composition-control parameters for friable materials  

SciTech Connect

A method for composition analysis of coal and minerals is proposed which uses scattered gamma radiation and does away with preliminary sample preparation to ensure homogeneous particle density, surface area, and size. Reduction of the error induced by material heterogeneity has previously been achieved by rotation of the control object during analysis. A further refinement is proposed which addresses the necessity that the contribution of the radiation scattered from each individual surface to the total intensity be the same. This is achieved by providing a constant linear rate of travel for the irradiated spot through back-and-forth motion of the sensor. An analytical expression is given for the laws of motion for the sensor and test tube which provides for uniform irradiated area movement along a path analogous to the Archimedes spiral. The relationships obtained permit optimization of measurement parameters in analyzing friable materials which are not uniform in grain size.

Pak, Yu.N.; Vdovkin, A.V.

1988-05-01

418

Hunting composite vector resonances at the LHC: naturalness facing data  

E-print Network

We introduce a simplified low-energy effective Lagrangian description of the phenomenology of heavy vector resonances in the minimal composite Higgs model, based on the coset SO(5)/SO(4), analysing in detail their interaction with lighter top partners. Our construction is based on robust assumptions on the symmetry structure of the theory and on plausible natural assumptions on its dynamics. We apply our simplified approach to triplets in the representations (3, 1) and (1, 3) and to singlets in the representation (1, 1) of SO(4). Our model captures the basic features of their phenomenology in terms of a minimal set of free parameters and can be efficiently used as a benchmark in the search for heavy spin-1 states at the LHC and at future colliders. We devise an efficient semi-analytic method to convert experimental limits on {\\sigma} {\\times} BR into bounds on the free parameters of the theory and we recast the presently available 8 TeV LHC data on experimental searches of spin-1 resonances as exclusion regions in the parameter space of the models. These latter are conveniently interpreted as a test of the notion of naturalness.

Davide Greco; Da Liu

2014-10-10

419

Curing Composite Materials Using Lower-Energy Electron Beams  

NASA Technical Reports Server (NTRS)

In an improved method of fabricating composite-material structures by laying up prepreg tapes (tapes of fiber reinforcement impregnated by uncured matrix materials) and then curing them, one cures the layups by use of beams of electrons having kinetic energies in the range of 200 to 300 keV. In contrast, in a prior method, one used electron beams characterized by kinetic energies up to 20 MeV. The improved method was first suggested by an Italian group in 1993, but had not been demonstrated until recently. With respect to both the prior method and the present improved method, the impetus for the use of electron- beam curing is a desire to avoid the high costs of autoclaves large enough to effect thermal curing of large composite-material structures. Unfortunately, in the prior method, the advantages of electron-beam curing are offset by the need for special walls and ceilings on curing chambers to shield personnel from x rays generated by impacts of energetic electrons. These shields must be thick [typically 2 to 3 ft (about 0.6 to 0.9 m) if made of concrete] and are therefore expensive. They also make it difficult to bring large structures into and out of the curing chambers. Currently, all major companies that fabricate composite-material spacecraft and aircraft structures form their layups by use of automated tape placement (ATP) machines. In the present improved method, an electron-beam gun is attached to an ATP head and used to irradiate the tape as it is pressed onto the workpiece. The electron kinetic energy between 200 and 300 keV is sufficient for penetration of the ply being laid plus one or two of the plies underneath it. Provided that the electron-beam gun is properly positioned, it is possible to administer the required electron dose and, at the same time, to protect personnel with less shielding than is needed in the prior method. Adequate shielding can be provided by concrete walls 6 ft (approximately equal to 1.8 m) high and 16 in. (approximately equal to 41 cm) thick, without a ceiling. The success of the present method depends on the use of a cationic epoxy as the matrix material in the prepreg tape, heating the prepreg tape to a temperature of 50 C immediately prior to layup, and exposing the workpiece to an electron-beam dose of approximately 2 Mrad. Experiments have shown that structures fabricated by the present method have the same mechanical properties as those of nominally identical structures fabricated by the prior method with electron beams of 3 to 4 MeV.

Byrne, Catherine A.; Bykanov, Alexander

2004-01-01

420

Predicting the tensile modulus and strength of single and hybrid natural fibre reinforced thermoplastic composites  

NASA Astrophysics Data System (ADS)

Natural fibre reinforced thermoplastics (NFRT) are used in a variety of commercial applications, but there is little theoretical modeling of structure/property relationships in these materials. In this thesis, micromechanical models available in the short-fibre literature were adapted to predict the tensile modulus and strength of some NFRT formulations. Hemp, 20 and 40-mesh hardwood, rice hulls and E-glass fibres were blended into HDPE to produce single and hybrid composites. Changes in fibre density and moisture content that occur during composite manufacturing were included in the micromechanical models. To account for fibre densification, the Young's modulus of the natural fibres was determined on a cell wall basis. A modified hybrid rule of mixtures (HROM) equation that uses experimental data from single NFRT was developed and found to adequately predict the tensile modulus of the hybrid composites. The tensile modulus for both the single and hybrid composites was found to linearly increase with an increase in fibre loading. The failure mechanism for all composite specimens was due to fibre pullout followed by matrix failure. Consequently the tensile strength of the NFRT was predicted using a ROM strength equation, which was modified with a derived semi-empirical fibre clustering parameter. The clustering parameter correctly predicted that as fibre loading increased, the average fibre stress would decrease. By assuming no contact between different types of fibres it was possible to use a modified HROM strength equation to predict the tensile strength of the hybrid composites. As a result parameters taken from the respective single fibre systems could be applied directly to the HROM equation. The modified ROM and HROM strength equations adequately predicted the tensile strength of various single and hybrid fibre reinforced composites over a wide range of composite loading. In this study experiments were conducted to shed light on the effect of a coupling agent (maleic anhydride) on the tensile strength and stiffness of various NFRT. Coupling agents, which alter the interfacial shear strength between the fibre and matrix, were determined to have a minimal effect on composite stiffness but produced increases in composite strength.

Facca, Angelo George

421

Structural Health Monitoring of Composite Materials Using the Two Dimensional Fast Fourier  

E-print Network

composite material that monitors its health using embedded micro-sensors and local network communicationStructural Health Monitoring of Composite Materials Using the Two Dimensional Fast Fourier. This work is part of an effort to develop smart composite materials that monitor their own health using

Nemat-Nasser, Sia

422

Composite Materials Instructor: Kenneth M. Golden, golden@math.utah.edu  

E-print Network

, concrete, and radar absorbing coatings. Calculating the bulk or effective material properties of compositesComposite Materials Instructor: Kenneth M. Golden, golden@math.utah.edu Professor of Mathematics, JWB 333 Abstract Composite materials appear throughout the sciences and engineering, particularly

Golden, Kenneth M.

423

Task 6.7.3 - Interfacial Mass Transport Effects in Composite Materials  

SciTech Connect

Advanced metal-matrix composites (MMCS) consisting of titanium-based alloys possess some unique mechanical, physical, and chemical characteristics that make them highly desirable for aircraft and gas turbine engines. Tailoring MMC properties is essential for advanced product design in materials processing. The main factors that affect materials processing and, further, the nature of a metal-ceramic interface, its structure, and morphological stability is liquid surface mass transport related to adhesional wetting physical effect) and reactive wetting (chemical effect). Surfaces and interfaces dominate many of the technologically important processes in composite materials such as liquid-solid sintering and joining. The objective of this work is threefold: 1) to get insight into the role of the nonstoichiometry of chemical composition in ceramic materials used as reinforcement components in MMC processing, 2) to extend previous energetic analysis of mass transport phenomena to wetting behavior between liquid metal and the quasi-solid like skin resulting from the presolidification of liquid on nonstoichiometric solids on a scale of interatomic distance, and 3) to provide experimental verification of our concept.

Jan W. Nowok

1998-02-01

424

Task 6.7.3 - Interfacial Mass Transport Effects in Composite Materials  

SciTech Connect

Advanced metal-matrix composites (MMCS) consisting of titanium-based alloys possess some unique mechanical, physical, and chemical characteristics that make them highly desirable for aircraft and gas turbine engines. Tailoring MMC properties is essential for advanced product design in materials processing. The main factors that affect materials processing and, further, the nature of a metal-ceramic interface, its structure, and morphological stability is liquid surface mass transport related to adhesional wetting (physical effect) and reactive wetting (chemical effect).' Surfaces and interfaces dominate many of the technologically important processes in composite materials such as liquid-solid sintering and joining. The objective of this work is threefold: 1) to get insight into the role of the nonstoichiometry of chemical composition in ceramic materials used as reinforcement components in MMC processing, 2) to extend previous energetic analysis of mass transport phenomena to wetting behavior between liquid metal and the quasi-solidlike skin resulting from the presolidification of liquid on nonstoichiometric solids on a scale of interatomic distance, and 3) to provide experimental verification of our concept.

Jan W. Nowok

1998-02-01

425

Statistical Characterization of Pultruded Composites with Natural Fiber Reinforcements – Part A: Fabrication  

Microsoft Academic Search

The objectives of this research are to demonstrate the feasibility of using the cost-effective pultrusion process to manufacture high quality polymeric composites using natural fiber reinforcements (NFR) and to quantify mechanical property variability for these composites. Natural fiber reinforcements offer value added properties such as the beneficial environmental impact of these renewable resources and the less abrasive nature of the

Ellen Lackey; James G. Vaughan; Kapil Inamdar; Brittany Hancock

2008-01-01

426

Smart composite materials for non-invasive structural health monitoring and composites manufacturing process monitoring  

NASA Astrophysics Data System (ADS)

Self-sensing composite materials with nanoscale sensor networks can provide feedback about quality evolution during composites manufacturing as well as long-term structural health. Multi-scale composites spanning nano to macro scales involve the interaction between components of varying length scales. An example of such an interaction is the influence of hollow glass microspheres on the electrical conductivity and strain sensitivity of novel carbon nanotube-based syntactic foams. In addition to uniformly dispersed carbon nanotube networks, selective integration of carbon nanotubes has been studied in form of carbon nanotube sheets and carbon nanotube sizing agents. Both techniques enable one-step carbon nanotube integration. Carbon nanotube sheets have been found to be especially useful for prepreg composites. In addition to piezoresistive-based sensing, time domain reflectometry has been studied and the strain response of time domain reflectometry sensors has been modeled and validated. Carbon nanotubes have been found to increase the strain response and damage sensitivity of time domain reflectometry sensors due to breakage of carbon nanotube networks. Two-dimensional deformation mapping and damage sensing has been implemented on composite panels using both piezoresistivity and time domain reflectometry. For the first time, high accuracy cure monitoring has been achieved using non-invasive time domain reflectometry sensors.

Pandey, Gaurav

427

Development of active and sensitive material systems based on composites  

NASA Astrophysics Data System (ADS)

This paper describes new concepts proposed by the author to realize active and sensitive structural material systems. Two examples of multifunctional composites were fabricated and evaluated in this study as follows: (1) An active laminate of aluminum plate (works as muscle), epoxy film (as insulator), unidirectional CFRP prepreg (as bone and blood vessel) and copper foil electrode (to apply voltage on CFRP) was made with an embedded optical fiber multiply fractured in the CFRP layer (works as nerve), of which curvature change could be effectively monitored with the fractured optical fiber. (2) A stainless steel fiber/aluminum active composite with embedded Ti oxide/Ti composite fiber was fabricated. The Ti oxide/Ti fiber could work as a sensor for temperature by removing a part of the oxide before embedment to make a metallic contact between the embedded titanium fiber and aluminum matrix to be able to generate thermal electromotive force, and also could work as a sensor for strain and as a heater for actuation. In the both cases, the outputs from their embedded sensors can be used to control their actuations.

Asanuma, Hiroshi

2002-07-01

428

Thermophysical characterization of composite materials under transient heating conditions  

NASA Technical Reports Server (NTRS)

Thermophysical property measurements were made under transient heating conditions on several materials being considered for use in SCOUT rocket motors. The materials included were ATJ graphite, MX 2600 silica phenolic, FM 5272 cellulose phenolic, and two carbon-carbon composites: CARBITEX 700 and RPP-4. The ATJ was included as a reference or base line material to check performance of the transient tests as it was not expected to be sensitive to heating rate. Measurements included in the program were thermal conductivity, strength, compressive stress-strain (carbon-carbon only), thermal expansion and the effective thermal expansion under partially restrained conditions. Development of this latter measurement was a major part of the program. It consisted of partially restraining the expansion of a specimen as it was heated, measuring the load and strain which occurred (together with a simultaneous modulus determination by superimposing a small cyclic load) and using these quantities to calculate what the effective thermal expansion would have to be to produce the observed stress and deformation. For materials which are sensitive to heating rate, such as reinforced phenolics, it was believed that this would provide a more realistic determination of the thermal expansion as it more nearly simulates the conditions experienced in end use.

Roetling, J.; Hanson, J.

1972-01-01

429

BIODEGRADATION OF COMPOSITE NONWOVENS MADE OF NATURAL FIBERS AND SYNTHETIC POLYMERS  

E-print Network

for biodegradation. For other compositions the presence of plasticizers used for reducing polymer crystallinity could1 BIODEGRADATION OF COMPOSITE NONWOVENS MADE OF NATURAL FIBERS AND SYNTHETIC POLYMERS Ioan I act as inhibitors for biodegradation, particularly in anaerobic conditions. Biodegradation

430

Engineering and characterisation of the interface in flax fibre\\/polypropylene composite materials. Part I. Development and investigation of surface treatments  

Microsoft Academic Search

Natural fibres have long been used as cost-cutting fillers in the plastics industry. Nowadays, they are considered to be a potential replacement of glass fibres for use in composite materials. However, although natural fibres have many advantages, the most important being their low cost and low density, they are not totally free of problems. A serious problem of natural fibres

N. E Zafeiropoulos; D. R Williams; C. A Baillie; F. L Matthews

2002-01-01

431

Water-responsive rapid recovery of natural cellular material.  

PubMed

Insight into the stimuli-responsive behaviour of biological materials with hierarchical microstructures is essential for designing new sustainable materials and structures. Shape memory, self-healing and self-repairing will become valuable characteristics of advanced materials. Here we report the water-triggered shape recovery of a natural biological material, the luffa sponge. The longitudinally crushed luffa sponge column can recover up to 98% of its original shape after it is immersed in water. The mechanical properties of the luffa sponge can also be recovered, to a large extent, after a subsequent drying process. The effects of strain rate, crushing strains, loading cycles, and temperature/duration of water treatment of the drying process on the shape recovery ratio and the energy dissipation recovery ratio have been investigated. The results from this study have demonstrated that the luffa sponge material possesses remarkable shape memory effects and mechanical recovery features which could be exploited or biomimicked for the design of water-responsive smart materials undergoing large deformations. PMID:24657743

Shen, Jianhu; Xie, Yi Min; Zhou, Shiwei; Huang, Xiaodong; Ruan, Dong

2014-06-01

432

Organic materials in planetary and protoplanetary systems: nature or nurture?  

NASA Astrophysics Data System (ADS)

Aims: The objective of this work is to summarize the discussion of a workshop aimed at investigating the properties, origins, and evolution of the materials that are responsible for the red coloration of the small objects in the outer parts of the solar system. Because of limitations or inconsistencies in the observations and, until recently, the limited availability of laboratory data, there are still many questions on the subject. Our goal is to approach two of the main questions in a systematic way: - Is coloring an original signature of materials that are presolar in origin ("nature") or stems from post-formational chemical alteration, or weathering ("nurture")? - What is the chemical signature of the material that causes spectra to be sloped towards the red in the visible? We examine evidence available both from the laboratory and from observations sampling different parts of the solar system and circumstellar regions (disks). Methods: We present a compilation of brief summaries gathered during the workshop and describe the evidence towards a primordial vs. evolutionary origin for the material that reddens the small objects in the outer parts of our, as well as in other, planetary systems. We proceed by first summarizing laboratory results followed by observational data collected at various distances from the Sun. Results: While laboratory experiments show clear evidence of irradiation effects, particularly from ion bombardment, the first obstacle often resides in the ability to unequivocally identify the organic material in the observations. The lack of extended spectral data of good quality and resolution is at the base of this problem. Furthermore, that both mechanisms, weathering and presolar, act on the icy materials in a spectroscopically indistinguishable way makes our goal of defining the impact of each mechanism challenging. Conclusions: Through a review of some of the workshop presentations and discussions, encompassing laboratory experiments as well as observational data, we infer that both "nature" and "nurture" are instrumental in the coloration of small objects in the outer parts

Dalle Ore, C. M.; Fulchignoni, M.; Cruikshank, D. P.; Barucci, M. A.; Brunetto, R.; Campins, H.; de Bergh, C.; Debes, J. H.; Dotto, E.; Emery, J. P.; Grundy, W. M.; Jones, A. P.; Mennella, V.; Orthous-Daunay, F. R.; Owen, T.; Pascucci, I.; Pendleton, Y. J.; Pinilla-Alonso, N.; Quirico, E.; Strazzulla, G.

2011-09-01

433

New composites based on poly(3-trimethylsilyltricyclononene-7) and organic nature fillers (calixarenes & cyclodextrins)  

NASA Astrophysics Data System (ADS)

Herein we describe new materials for membrane gas separation process with improved selectivities towards different pairs of gases. Organic nature fillers (modified calix[4]arenes, calix[8]arenes and modified ?-, ?-, ?-cyclodextrins) were used as additives to poly(trimethylsilyltricyclononene-7) (PTCNSi1)in order to study correlations between structure of the filling agent and gas transport parameters of the composite membranes. It was shown a positive influence of calixarenes and cyclodextrins as additives on permselectivity of the membranes. For instance, selectivity towards H2/CH4 gas pair increased almost in 2.4 times when calix[4]arene with Et- and tert-Bu- group was introduced into polymeric matrix. Detailed study of the PTCNSi1 adsorbtion/desortion data is presented. The obtained composites were characterized by TEM, WAXD, PALS and BET analysis.

Chapala, Pavel P.; Bermeshev, Maxim V.; Starannikova, Ludmila E.; Gavrilova, Natalie N.; Shantarovich, Victor P.; Filatova, Marina P.; Krut'ko, Ekaterina B.; Yampolskii, Yurii P.; Finkelshtein, Eugene Sh.

2014-05-01

434

Hydrogen Permeability of a Polymer Based Composite Tank Material Under Tetra-Axial Strain  

NASA Technical Reports Server (NTRS)

In order to increase the performance of future expendable and reusable launch vehicles and reduce per-pound payload launch costs, weight reductions have been sought in vehicle components. Historically, the cryogenic propellant tanks for launch vehicles have been constructed from metal. These are some of the largest structural components in the vehicle and contribute significantly to the vehicles total dry weight. A successful replacement material will be conformable, have a high strength to weight ratio, and have a low gas-permeability to the cryogens being stored, i.e., oxygen and hydrogen. Polymer-based composites are likely candidates to fill this role. Polymer and polymer-based composites in general are known to have acceptable gas permeation properties in their as-cured state.1 The use of polymer-based composites for this application has been proposed for some time.2 Some successes have been reported with oxygen3, but other than the DC-XA experience, those with hydrogen have been limited. The primary reason for this has been the small molecular diameter of hydrogen, the lower temperatures of the liquid, and that the composite materials examined to date have all been susceptible to microcrack formation in response to the thermal-mechanical cycles experienced in the use-environment. There have been numerous accounts of composite materials with reported acceptable resistance to the formation of microcracks when exposed to various mechanical and/or thermal cycles. However, virtually all of these studies have employed uniaxial loads and there has been no discussion or empirical evidence pertaining to how these loads relate to the biaxial state of stress in the material in its use environment. Furthermore, many of these studies have suffered from a lack of instrument sensitivity in detecting hydrogen permeability, no standards, insufficient documentation of test conditions, testing of cycled materials in their unload state, and/or false assumptions about the nature of the microcracks in the material. This paper documents the results of hydrogen permeability testing on a Bismaleimide (BMI) based graphite fiber composite material under a variety of tetra-axial strain states.

Stokes, Eric H.

2003-01-01

435